About this course:
This course reviews nationwide and worldwide statistics regarding immunizations and their efficacy in reducing morbidity and mortality. In addition, this course reviews the recommended immunization schedules for children and adults in the US, including contraindications and safety considerations with pregnancy. Finally, this course reviews the use of immunizations for worldwide epidemics and discusses the phenomenon of vaccine hesitancy.
This course reviews nationwide and worldwide statistics regarding immunizations and their efficacy in reducing morbidity and mortality. In addition, this course reviews the recommended immunization schedules for children and adults in the US, including contraindications and safety considerations with pregnancy. Finally, this course reviews the use of immunizations for worldwide epidemics and discusses the phenomenon of vaccine hesitancy.
After this activity, learners will be prepared to:
- Recall the current nationwide and worldwide statistics regarding immunizations
- Identify examples of the efficacy of immunizations in reducing morbidity and mortality
- Describe the components of the recommended immunization schedules for children and adults in the US
- Discuss the safety of various immunizations during pregnancy
- Describe the use of immunizations in such worldwide epidemics as dengue fever, malaria, and cholera
- Discuss the phenomenon of vaccine hesitancy and the myths surrounding the COVID-19 vaccine
The World Health Organization (WHO, 2019a, 2021c) asserts that immunizations or vaccines (these terms will be used interchangeably throughout this learning experience) are the most cost-effective health intervention. Immunizations prevent 4-5 million deaths per year worldwide, and if global coverage increases, it is predicted that an additional 1.5 million deaths could be prevented. Expanding access to immunizations is critical to preventing sickness and death associated with infectious diseases such as polio, tetanus, whooping cough, and measles. However, global immunization coverage has plateaued over the last decade and dropped from 86% to 83% in 2020. It is estimated that almost 23 million children worldwide (i.e., the highest number since 2009) under the age of one did not receive the basic immunizations. Approximately 60% of these children live in Angola, Brazil, the Democratic Republic of the Congo, Ethiopia, India, Indonesia, Nigeria, Pakistan, the Philippines, and Vietnam. In addition, completely unvaccinated children increased by 3.4 million in 2020. The COVID-19 pandemic has led to significant disruptions in the healthcare system, contributing to the recent increase in missed vaccines. These numbers are expected to worsen as many countries focus on controlling the pandemic (WHO, 2019a, 2021c). Healthcare providers (HCPs) should be aware of the following terminology:
- A vaccine is a preparation used to stimulate the immune response against disease. These are usually administered through intramuscular injection, but some can be administered orally or nasally.
- Vaccination refers to the act of introducing the vaccine into the body.
- Immunization refers to how a person becomes protected (i.e., through vaccination) from a specific disease. Immunization is often used interchangeably with vaccination or inoculation.
- Immunity refers to protection from an infectious disease (i.e., you can be exposed without becoming infected; CDC, 2021d).
Principles of Immunization
Immunization is a vital part of public health and disease prevention, significantly contributing to increased life expectancy and improved quality of life (QOL). The first vaccine was administered in 1796 when a 13-year-old boy was inoculated with cowpox, resulting in immunity to smallpox. Smallpox was globally eradicated in 1979 because of immunization. Knowing how the body fights infections is important to understanding how vaccines work. Once a pathogen invades, the body activates defenses to protect itself from the foreign object and kill the invader. The invasion and multiplication of foreign materials eventually lead to an active infection. As a result, the body produces and releases different cells designed to combat the disease. The main components of the immune response come from white blood cells such as macrophages, B-lymphocytes, and T-lymphocytes. Macrophages are phagocytic, engulfing and digesting foreign material, including pathogens. A small portion of the pathogen, known as an antigen, remains during this process. The role of the B-lymphocytes is to create matching antibodies based on the antigen. The role of the T-lymphocytes is to attack host cells that the pathogen has already invaded to prevent further infection or illness (CDC, 2018b; Ginglen & Doyle, 2021).
A vaccine is a pharmacologic compound that improves immunity to various diseases by mimicking a specific disease's invasion of the body. Vaccines contain a form of the disease-causing agent (i.e., weakened or dead form, inactivated version of the toxin, or a protein from the microbe's surface). Introducing the agent into the body allows the immune system to quickly recognize the antigen as foreign and develop antibodies and memory T-lymphocytes. The process enables the body to mount a robust and rapid immune response if exposed to the disease again. After an individual receives a vaccination, they may experience chills, fever, body aches, pain at the injection site, and fatigue caused by the immune system working to fight the foreign material contained in the vaccine. It does take the body up to a few weeks to create the T-lymphocytes and B-lymphocytes following vaccination. Therefore, if an individual is exposed to the disease before the body achieves immunity, they can still become sick with the condition they were recently vaccinated against (CDC, 2018b; Ginglen & Doyle, 2021; Hibberd, 2021; Justiz Vaillant & Grella, 2021).
Most vaccines induce active immunity by promoting the development of antibodies via a primary immune response. Therefore, if an individual is subsequently exposed to the pathogen, a secondary response occurs, increasing antibody formation (resulting in increased protection). However, some vaccines require boosters to sustain protection. Passive immunization involves the administration of antibodies known as immune globulin, derived from pooled human serum or antitoxin harvested from immunized animals. Passive immunity is used for immunocompromised individuals who cannot mount an effective immune response. However, passive immunity is less commonly recommended for healthy adults and only offers short-term protection (Ginglen & Doyle, 2021; Hibberd, 2021; Justiz Vaillant & Grella, 2021).
Types of Vaccines
There are many ways to create a vaccine. The most common vaccinations are live attenuated, inactivated, toxoid, subunit, mRNA, and conjugate. Live attenuated vaccines contain live viruses or bacteria that have been weakened to prevent an active infection in an individual with a healthy immune system. Since these vaccines contain a live version of the germ, they create an immune response and memory similar to naturally acquired immunity. Examples of live attenuated vaccines include MMR and varicella. Since these vaccines contain live material, they are contraindicated in immunocompromised patients (CDC, 2018b).
Inactivated vaccines are also created to protect against bacteria and viruses, but the virus or bacteria is killed or inactivated during production. An example of this type of vaccine is the inactivated polio vaccine (IPV) which contains an inactivated form of the poliovirus. Since these vaccines contain inactivated forms of the virus or bacteria, the process of creating immunity is different than what occurs when an individual is given a vaccine that contains live attenuated bacteria or viruses; therefore, multiple doses are required at set intervals known as a series (CDC, 2018b).
Toxoid vaccines are specifically designed to protect an individual against a bacterium that produces toxins once it enters the body. During the production of these vaccines, the toxin is weakened to the point that it cannot cause illness. The weakened form of the toxin is known as a toxoid. The toxoid vaccine al
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The DTaP vaccine also contains a subunit vaccine for acellular pertussis. Subunit vaccines also contain essential material from the pathogen; therefore, side effects following vaccination are less common. The acellular pertussis vaccine contains inactivated pertussis toxin and one or more bacterial components. This was developed in the 1980s in response to a high rate of complications reported after administering the previously used whole-cell (inactivated) pertussis vaccine (CDC, 2018b).
Messenger RNA (mRNA) vaccines work by teaching our cells how to make a protein that will trigger an immune response in the body. This immune response will produce antibodies that will protect the individual if the actual virus enters the body. mRNA vaccines are newly available to the public, specifically for the COVID-19 virus. Instead of using weakened or inactivated germs, the vaccine uses mRNA created in a laboratory that instructs the cells to a spike protein found on the virus's surface. Once the spike protein Is made, the cells break down and remove the mRNA (CDC, 2022c).
The last type of vaccination is a conjugate vaccine. These types of vaccines protect against bacteria that have a polysaccharide outer coating. This coating makes it more difficult for the immune system to recognize the pathogen. This is especially true in children since they have less mature immune systems. These vaccines connect or conjugate the polysaccharide coating on the bacteria to antigens that the immune system recognizes and has an effective response against. This helps the immune system develop the appropriate response to bacteria with a polysaccharide coating. An example of a conjugate vaccine is the Hib vaccine (CDC, 2018b).
Vaccines can prevent various illnesses, from influenza and diarrhea to cervical cancer and paralysis related to polio. Polio, for example, was once a highly infectious viral disease that could cause irremediable paralysis. Globally targeted for eradication, polio has been nearly eliminated via immunization efforts, existing now in just a few small regions of Pakistan, Nigeria, and Afghanistan. However, until polio transmission is interrupted in these countries, all countries remain at risk due to travel links to endemic areas. In addition, only 83% of infants worldwide received three doses of the polio vaccine in 2020 (WHO, 2019a, 2021c).
Tetanus is caused by a bacterium that can grow from spores of C. tetani which is present in the environment. The toxin produced can cause severe complications and death. Infection risk persists as a public health problem in 12 countries, mainly in Asia and Africa. In 2018, approximately 86% of children worldwide under the age of one year received three doses of diphtheria, tetanus, and pertussis (DTaP) vaccine (WHO, 2019a, 2021c).
The effectiveness of immunizations varies from vaccine to vaccine and from condition to condition. As stated above, some vaccines (e.g., polio) are very effective at eradicating the disease. Others are adjunctive tools in a large public health toolbox. For example, meningitis A is an infection that can cause severe brain damage and death. The meningitis A vaccine, introduced in 2010 in sub-Saharan Africa, has nearly eliminated that infection in less than ten years. However, the meningitis A vaccine is not being integrated into routine worldwide immunization programs. Measles is a highly contagious virus that causes high fevers and rash and can lead to disability, infection, and death. Accelerated immunization efforts have led to a global decrease of 73%, from 536,000 in 2000 to 142,000 cases in 2018 (WHO, 2019a, 2021a).
The WHO estimates that 500,000 children under the age of 5 die from Streptococcus pneumoniae each year worldwide, mostly in Africa and Asia. The original vaccine against S. pneumoniae, PCV7, was introduced in the US in 2000 and Africa in 2009. The vaccine was upgraded to include more serotypes, renamed PCV13, and reintroduced in 2010/2011. In 2022, PCV 15 and PCV 20 were approved for use in adults 19 years and older. Rates of pneumococcal infections in South Africa in children under the age of two decreased from 54.8 cases per 100,000 person-years before the vaccination (2005-2008) to just 17 cases per 100,000 person-years after (2011-2012) thanks to a vaccination coverage of 81% in 2012. Despite progress, approximately 74 million (55%) of the worldwide infant population are still not receiving the pneumococcal vaccine (CDC, 2020a; von Gottberg et al., 2014).
The outcome of introducing new vaccines can be measured in fundamental shifts or changes in medical care trends and outcomes. For example, the varicella vaccine (Varivax or VAR) was introduced in the US in 1995, with 89% vaccine coverage nationwide by 2006. Zostavax (ZVL) was a live attenuated vaccine introduced in 2006 for herpes zoster or shingles, a secondary infection related to the same virus. The sale and use of the ZVL vaccine were discontinued in the US in 2020. While the VAR vaccine is recommended for children, the Shingrix vaccine is recommended for people over 50. A study published in 2017 found that between 2006 and 2013, there was a 39% decrease in emergency department visits for infection with the herpes zoster virus in people under age 20 (who would be covered by the VAR vaccine) and an 11% decrease over the same time for people over age 60 (covered by the ZVL vaccine). The authors felt confident that this decreased utilization of costly emergency department resources was related to effective immunizations in the younger and older age groups. However, the researchers found a 23% increase in people ages 20-59 who would not be candidates for either vaccine. Rotaviruses are the leading cause of severe diarrhea in young children, with global coverage of about 46%. A cross-sectional ecological study conducted in southern China found that incidence rates decreased and the age of onset increased as an oral rotavirus vaccination (RV) was introduced (Dommasch et al., 2017; Fu et al., 2018; WHO, 2021c).
Closer to home, two separate studies have shown encouraging trends related to cervical cancer since the 2006 introduction of the controversial vaccination for human papillomavirus (HPV). HPV is the most common viral infection of the reproductive tract; it can cause genital warts in men and women and cervical cancer in women. A retrospective cohort study between 2007 and 2014 across 16 clinics serving predominantly low-income and minority populations showed a decrease in abnormal cervical cytology. The detection rate for vaccinated girls (at least one dose, ages 11-20) decreased to 79.1 per 1000 person-years, versus 125.7 per 1000 person-years amongst those not vaccinated. This effectiveness was most apparent amongst those who initiated the vaccine series between the recommended ages of 11-14 and received all three doses (Hofstetter et al., 2016). Similarly, Benard and colleagues (2017) found a decrease of cervical intraepithelial neoplasia (CIN) amongst girls aged 15-19 in New Mexico over the same period. The incidence per 100,000 women screened decreased from 3,468.3 in 2007 to 1,590.6 in 2014 for CIN1, from 896.4 to 414.9 for CIN2, and 240.2 to 0 for CIN3. The researchers found a similar significant decrease in CIN2 lesions amongst women ages 20-24, but an increase in CIN1 and CIN3 lesions amongst women aged 25-29, who would not have benefited from vaccination before age 14 as recommended. Although research has supported the effectiveness of the HPV vaccine, many large countries have not introduced the vaccine, resulting in decreased coverage (Benard et al., 2017; CDC, 2021d).
In 2019, a novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was identified In Wuhan, China. In 2020, the WHO named this disease COVID-19 as it quickly spread worldwide, resulting in a global pandemic. By the end of 2020, several vaccines became available worldwide to help prevent the spread of COVID-19. All the available vaccines are highly effective in reducing the risk of COVID-19, specifically reducing the risk for severe disease, hospitalization, and death. Even with the emergence of new variants, the COVID-19 vaccines mitigate the risks of severe disease. Numerous clinical trials report on the safety, efficacy, and effectiveness of the various COVID-19 vaccines; however, there is limited research comparing the efficacy of the vaccines to each other. According to the CDC, the mRNA vaccines are recommended over the adenoviral vector vaccines based on the more favorable risk-benefit profile of the mRNA vaccines. More specifically, the adenoviral vector vaccines have been associated with thrombosis with thrombocytopenia and Guillain-Barre syndrome (GBS), whereas the mRNA vaccines have been associated with myocarditis. The risk of these events is minimal; therefore, adenoviral vaccines are recommended if mRNA vaccines are not available. Equitable access to the COVID-19 vaccine is critical to ending the global pandemic (Edwards & Orenstein, 2022; WHO, n.d.).
In their latest report, the CDC reported vaccination rates of children at 24 months old born in 2017 and 2018. Compared to those born between 2015 and 2016, vaccination rates mainly remained the same, with some increases (see Figure 1). Although the overall vaccination rate did not decrease, there was an increase in the disparity between those children that received vaccinations and those that did not. The most considerable gap was between children with private insurance and those without, and the most significant vaccination disparity was for influenza and rotavirus. The rate of uninsured children who were unvaccinated by 24 months was 3.3%, while the percentage of children with private insurance unvaccinated by 24 months was 0.8%. Although the data has not been released yet, there are concerns regarding the COVID-19 pandemic and its effects on the rate of routine vaccination in children (Hill et al., 2021).
Adult and Child Immunization Schedules
The CDC puts forth the immunization recommendations and schedules in the US based on the Advisory Committee on Immunization Practices (ACIP) policies. The recommended child (ages 18 years or younger) and adult (ages 19 years and older) immunization schedules for the US can be found in Figure 2 and Figure 3.
Influenza or flu is a single-stranded RNA virus belonging to the orthomyxovirus family that can lead to serious illness, hospitalization, or death. Each season the flu is slightly different, and it affects millions of people, with hundreds of thousands needing hospitalization. Complications can arise from influenza infection, including bacterial pneumonia, ear and sinus infections, and exacerbations of chronic respiratory illnesses such as asthma and COPD. Receiving a yearly flu vaccine is the best way to prevent influenza infection and decrease the likelihood of hospitalization. Three different types of influenza are known to infect humans: A, B, and C. Children are most commonly infected with influenza B. Influenza is transmitted from person to person via large respiratory droplets and has an incubation period of 1-4 days. The onset of symptoms may occur suddenly and include cough, sore throat, runny nose, fever, chills, headache, malaise, vomiting, and diarrhea (Hall, 2021).
The influenza vaccine is available in multiple forms: an inactivated (IIV), recombinant (RIV), or live attenuated influenza vaccine (LAIV). Some influenza vaccines are produced by growing the virus inside chicken eggs. Due to this production process, the vaccine may contain trace amounts of egg protein. Egg-free options include the cell-culture-based IIV and the RIV4 (Flublok). Individuals with an egg allergy are still able to receive any of the influenza vaccines approved for use in their age group; however, those that experience severe allergic reactions need to receive the vaccination in a healthcare setting under the supervision of an HCP that can recognize and manage a severe allergic reaction. Adverse effects following vaccination include injection site soreness and swelling, headache, fatigue, and muscle pain (CDC, 2021e).
The CDC recommends the IIV annually for anyone over six months old. It is administered intramuscularly and is available as a quadrivalent vaccine (containing four influenza virus strains). Each brand has a recommended age range. For children under the age of 8 receiving their first-ever influenza vaccination, two doses (IIV) should be given at least four weeks apart. It is recommended that children are vaccinated as soon as the yearly vaccination is made available to ensure immunity before an influenza outbreak in the individual’s community. The highest numbers of influenza cases occur during February and March; therefore, vaccination is recommended even if flu season has already begun. The RIV (Flublok) is a quadrivalent vaccine for adults over 18 given intramuscularly. LAIV (FluMist)is a quadrivalent nasal spray approved for use between 2 and 49 years old. LAIV should not be given to individuals with a history of severe allergic reaction to any vaccine component (excluding egg) or a previous dose of any influenza vaccine. In addition, it should not be given to individuals who are immunocompromised, have anatomic or functional asplenia, are pregnant, have cochlear implants, or have cranial cerebrospinal fluid/oropharyngeal communications (CDC, 2021e, 2022a; WHO, 2021c).
The CDC recommends that all HCPs are vaccinated for influenza annually to help prevent the spread of the disease to patients, coworkers, and families. Some healthcare systems have started requiring employee vaccination or proof of vaccination off-site. In a nationwide survey, the number of hospital systems surveyed requiring influenza vaccination increased from 37% in 2013 to 61% in 2017. Unfortunately, only 3 of 73 Veterans Affairs (VA) hospital systems required influenza vaccination amongst HCPs in 2017 (Greene et al., 2018). See the Nursing CE course Influenza: Signs, symptoms, treatment, and prevention for more information on influenza.
Tetanus, Diphtheria, Pertussis
Diphtheria, tetanus, and pertussis are different diseases preventable with one vaccination. Diphtheria is an infection of the nose and throat caused by a bacterium that can lead to difficulty breathing, heart failure, paralysis, and even death. Tetanus is an infection caused by a bacterium toxin that affects the nervous system and can lead to lockjaw, difficulty breathing, and death. Pertussis, or whooping cough, is a respiratory infection caused by Bordetella pertussis resulting in uncontrollable and sometimes violent coughing paroxysms, making breathing difficult. Pertussis is most serious in infants and young children and can lead to pneumonia, brain damage, and even death. The CDC recommends that everyone be vaccinated against tetanus, diphtheria, and pertussis. The diphtheria and tetanus portions of the vaccine contain a toxoid, and the pertussis portion is a subunit vaccine with acellular pertussis bacteria components and inactivated pertussis toxin. Vaccine coverage in the US in 2015 was 95% for three or more doses and 85% for four or more doses. Effectiveness for the series of five is 88.7% against pertussis but wanes over time (CDC, 2021d, 2021k; Wood et al., 2018).
For children, there are two vaccinations available for diphtheria, tetanus, and pertussis: DTaP (used to provide immunity) and Tdap (used to boost immunity). DTaP is approved in the US for use in children younger than 7. It is recommended that infants receive three doses of the DTaP vaccine at 2, 4, and 6 months old. After this initial series, children should receive a booster dose at 15-18 months and again at 4-6 years for five total doses. The Tdap vaccine contains smaller diphtheria toxoid and pertussis components and focuses on the tetanus toxoid. To boost immunity, all children between the ages of 11 and 12 should receive a dose of Tdap. The DTaP vaccine provides 98% protection against pertussis for the first year following vaccination and approximately 71% coverage for the next 5 years. The DTaP and Tdap vaccinations effectively prevent tetanus and diphtheria for approximately 10 years following vaccine administration. The DTaP vaccine is contraindicated in children with a prior history of allergic reaction to the vaccine or one of its components and those with a prior history of encephalopathy not attributable to another cause within 7 days of a previous DTaP dose. Precaution is advised in those with a prior history of GBS, Arthus-type hypersensitivity reactions, progressive neurological disorders, or in those with a moderate to severe acute illness (CDC, 2021k).
Two vaccines are available for adults, Tdap (Adacel, Boostrix) and tetanus-diphtheria (Td, Tenivac, Tdvax). Adults who did not receive a Tdap booster as an adolescent can be given one dose as an adult, followed by a tetanus-diphtheria (Td) or Tdap booster vaccine every ten years. For wound management in adults, HCPs should consider Tdap or Td administration. Tdap or Td should be administered for clean or minor wounds if it has been more than 10 years since the last Tdap or Td. For all other wounds, administer Tdap or Td if it has been more than 5 years since the previous Tdap or Td or if the vaccination status cannot be verified. For women, this vaccine was recommended beginning in 2012 to be given during each pregnancy to help protect the fetus and newborn, especially susceptible to pertussis infection during the first eight weeks of life (CDC, 2022a; Liang et al., 2018). The CDC recommends that Tdap be given between 27- and 36-weeks’ gestation. As an alternative to vaccinating pregnant women, a randomized clinical trial tested the use of an acellular pertussis vaccine in newborns under five days old and found no safety issues with this. In addition, the researchers found a statistically significant increase in pertussis IgG levels in the newborns who received the vaccine through 10 weeks. However, there was some concern that they found decreased IgG levels for other vaccines at 32 weeks of age, calling into question immune interference from an additional vaccine (CDC, 2022a; Wood et al., 2018). The Td and Tdap are contraindicated in those with a history of a severe allergic reaction after a prior dose. The Tdap is also contraindicated in those with a prior history of encephalopathy not attributable to another cause within 7 days of a previous DTaP, DTP, or Tdap dose. Precaution is advised in those with a prior history of GBS, Arthus-type hypersensitivity reactions, progressive neurological disorders, or in those with a moderate to severe acute illness (CDC, 2022a).
Measles, Mumps, and Rubella (MMR)
Measles (often referred to as rubeola) is a highly contagious virus transmitted via droplets when coughing or sneezing. A measles infection begins with a cough, runny nose, fever, and red eyes. As the disease progresses, small red spots appear on the skin, starting on the head and eventually spreading caudally (Gastanaduy et al., 2021). Mumps is a viral infection characterized by swollen parotid glands and fever, headache, body aches, and can lead to viral meningitis (Marlow et al., 2021). Rubella (also German measles) is a mild viral infection in children that typically causes a fever, sore throat, and rash that originates on the face and spreads across the body. Rubella can be highly dangerous in pregnant women, especially if contracted in the first trimester, potentially causing a miscarriage or severe congenital disabilities if the unborn child survives (Lanzieri et al., 2021). Internationally, the measles vaccination is available in 179 countries with single-dose worldwide coverage of 84% and two-dose coverage of 70% worldwide. Deaths related to measles have decreased by 84%, from 550,000 in 2000 to 89,780 in 2016. The mumps vaccine is currently only available in 123 countries worldwide, while the Rubella vaccine is available in 173 countries with global coverage of 70% (CDC, 2021d; WHO, 2021c).
The vaccine used to prevent all three diseases is known as the MMR vaccine, named for the three diseases. There are two vaccinations available for use in the US: M-M-R II and ProQuad. M-M-R II is an MMR vaccine and ProQuad also contains varicella, MMRV. Both vaccines contain live, attenuated measles, mumps, and rubella virus. It is recommended that children receive two doses, the first at 12-15 months old and the second at 4-6 years old. If a child receives a dose of the MMR vaccine before 12 months due to international travel or a community-wide outbreak of measles, mumps, or rubella, two doses should still be administered at 12-15 months and 4-6 years. The MMR vaccine is very effective at preventing all three diseases. After receiving both doses, the MMR is 97% effective at preventing measles and 88% effective at preventing mumps. Individuals who receive both doses are considered immune for life against measles and rubella. Immunity to mumps does decrease over time (CDC, 2021f).
The routine MMR vaccination for adults (19-64 years) with no evidence of immunity (i.e., born after 1957) is one dose. For patients with HIV, HCPs, and students in postsecondary institutions or international travelers, a 2-dose series 4 weeks apart is recommended. MMR and MMRV are contraindicated in patients that have had an allergic reaction to previous doses of the vaccine or any component of the vaccine, are severely immunocompromised (as it is a live, attenuated vaccine), or have a family or personal history of immunodeficiency. Specifically, the MMR is contraindicated in pregnant women, individuals with HIV with a CD4 count of fewer than 200 cells/mm3, and severe immunocompromising conditions. In addition, vaccination should not occur for 1 month following treatment with systemic high-dose corticosteroids for over 14 days and 3-11 months after receiving antibody-containing blood products. Adverse reactions following administration of MMR include fever greater than 103°F, rash, arthralgia, febrile seizures, and anaphylactic reaction (CDC, 2022a; Marlow et al., 2021; WHO, 2021c).
The varicella-zoster virus (VZV) is a member of the herpesvirus family. Primary infection with VZV causes a highly contagious disease known as varicella or chickenpox. VZV enters the body via the respiratory tract and conjunctiva. Once infected, the disease causes an itchy, blistering rash that first appears on the face and trunk and spreads to the extremities. The rash rapidly progresses from macules to papules to vesicular lesions. Symptoms tend to be mild in children, and recovery usually results in lifetime immunity; however, VZV can remain in the body as a latent infection. VZV used to be a widespread childhood illness until the varicella vaccination became available in the US in 1995. Before widespread vaccine use, 4 million people contracted chickenpox annually, with approximately 13,000 of those requiring hospitalization and over 150 deaths (Lopez et al., 2021).
There are two formulations of the chickenpox vaccine. VAR (Varivax) only contains the chickenpox vaccine, while MMRV (ProQuad) combines varicella with MMR. For any individual that has not had chickenpox or received a vaccination, the CDC recommends two doses of the varicella vaccine. The first dose is recommended at 12-15 months and the second at 4-6 years old. When administering catch-up doses, the administrations should be spaced at least 3 months in children ages 7-13 and 4 weeks in individuals over 13. Varicella vaccination is contraindicated in any individual with a history of anaphylactic reaction to a previous dose of the vaccine or any component of the vaccine including gelatin and neomycin, diagnosed with leukemia, lymphoma, malignant neoplasm of the bone marrow or lymphatic system, primary or acquired immunodeficiency – including HIV, are receiving immunosuppressant or high-dose corticosteroid medications, pregnant, or suffering from a moderate to severe illness. For 14 days after vaccination, individuals should not receive blood products unless the need for blood outweighs immune protection against VZV. Typically, administering salicylates is contraindicated for 6 weeks following varicella vaccination due to the risk of Reye syndrome; however, vaccination is possible in children diagnosed with rheumatoid arthritis or another disorder requiring administration of salicylates, under close monitoring by an HCP (CDC, 2021n). After administration, the most common adverse effects include fever greater than 102°F, rash, injection site tenderness, and edema. Administration of the MMRV has an increased incidence of fever-induced seizures compared to administering the MMR and varicella vaccines separately (Lopez et al., 2021).
The VAR vaccine is recommended for adults with no evidence of immunity to varicella (i.e., born after 1980 or no documented evidence of varicella-containing vaccine). The VAR vaccine is administered in a 2-dose series 4-8 weeks apart if the person did not previously receive a varicella-containing vaccine. If the person previously received one dose of varicella-containing vaccine, a second dose is administered at least 4 weeks after the first. A similar administration schedule should be used for HCPs. For persons with HIV, two doses of the VAR vaccination may be considered three months apart (CDC, 2022a).
Herpes Zoster Recombinant (RZV)
Herpes zoster vaccines are exclusively for use in adults to prevent shingles. Zostavax (ZVL) is a live vaccine previously approved for age 60 or above administered as a single dose but is no longer available in the US (as of November 2020). ZVL was available starting in 2006 and could not be given to immunocompromised patients because it was a live vaccine. Shingrix (RZV) is a recombinant vaccine approved as a two-dose series that should be given 2-6 months apart at 50 years and older. RZV was approved for use in 2017. It reduces the risk of shingles or postherpetic neuralgia by 90% and is thus preferred by the CDC. It is also safe for immunocompromised patients. RZV is recommended for use in patients over 18 who are (or will be) immunosuppressed due to disease or therapy. If ZVL was previously given, RZV should be given at least 2 months (8 weeks) after ZVL (CDC, 2022a, 2022b). The RZV vaccine is contraindicated in those with a prior history of allergic reaction to the vaccine or one of its components. Precaution is advised in those with a moderate to severe acute illness or current herpes zoster infection (CDC, 2022a).
Human Papillomavirus (HPV)
HPV is the most common sexually transmitted infection in the US. Although most individuals infected with HPV are asymptomatic, the virus can cause reproductive and oral cancers later in life. The HPV vaccine prevents genital warts and many types of cancer, including cervical, oropharynx, anal, penile, vaginal, and vulvar cancer. The cost for 8 million vaccine doses is estimated at $1.6 billion, while the estimated treatment cost for HPV-associated disease is $8 billion (Moreno, 2019). Before HPV vaccine approval, there were 14 million new cases of HPV per year in the US. Since the HPV vaccination was first approved in 2006, infection with the types of HPV that cause cancers and genital warts has decreased 86% in teenage girls and 71% in young adult women ages 20-24, and protection has lasted long-term (Meites et al., 2021).
The only vaccine currently available against HPV (Gardasil-9) is a recombinant vaccine that protects against nine different HPV types. The CDC recommends that the first dose of HPV vaccine be given between 11-12 years old, with the second dose given 6-12 months later; however, the series can start in individuals as young as 9 years old. Only two doses are required if both doses are given before an individual’s 15th birthday. If the series is not finished before an individual turns 15, three doses of the vaccine are recommended through 26 years old. Contraindications to vaccine administration include anaphylaxis to a previous dose of the HPV vaccine or any of its components, including yeast, since Gardasil-9 is produced in baker’s yeast. Following vaccination, common adverse effects include local reactions (pain, tenderness, swelling), fever above 100°F, malaise, nausea, dizziness. Syncope is also common following vaccination; therefore, the patient should be seated or lying down during administration until 15 minutes after. In addition, the HPV vaccine can be given to adults 27 to 45 years old based on shared clinical decision-making. After the initial dose, the vaccine should be repeated at 1 to 2 months and 6 months. The series is not restarted if the vaccination schedule is interrupted. For persons with HIV or other immunocompromising conditions, a 3-dose series Is recommended regardless of age at initial vaccination (CDC, 2021c, 2022a). For more information on HPV, see the Nursing CE course on human papillomavirus.
Pneumococcal (PCV13, PCV15, PCV20, PCV23)
PCV13 is a conjugate vaccine against 13 different pneumococcal bacteria that can cause meningitis, pneumonia, febrile bacteremia, otitis media, sinusitis, or bronchitis in children. It is currently available in 151 countries, but coverage is only 49% worldwide. PCV13 was approved for use in 2010 and replaced the PCV7 vaccine, which was introduced in 2000 and protected against seven types of pneumococcal bacteria. It has been estimated that in the first three years following introduction, the use of PCV13 has prevented over 30,000 cases of pneumococcal disease and over 3,000 deaths (Gierke et al., 2021; WHO, 2021c). On October 20, 2021, the ACIP recommended 15-valent PCV (PCV15) or 20-valent PCV (PCV20) for adults at least 65 years old or 19–64 years old with certain underlying conditions who have not previously received a pneumococcal vaccine. When PCV15 is used, it should be followed by a dose of PPSV23, typically at least a year later. Both PCV15 and PCV20 were approved for adults over 18 in 2021 by the FDA (Kobayashi et al., 2022).
The CDC recommends that children receive PCV13 at 2, 4, 6, and 12-15 months old to be fully vaccinated. Side effects after administration include pain and swelling at the injection site, decreased appetite, lethargy, headache, irritability, and fever. PCV13 should not be administered to anyone with a history of severe allergic reaction to a previous dose of the vaccine or any component, including diphtheria toxoid. HCPs must be cautious administering PCV13 to any individual experiencing a moderate to severe acute illness. Although not contraindicated, studies have shown that simultaneous administration of PCV13 and inactivated influenza vaccine increased the risk of febrile seizures in young children. Children diagnosed with sickle cell disease, CSF leak, liver disease, chronic heart disease, or have a cochlear implant are at a higher risk for infection with invasive pneumococcal disease (Gierke et al., 2021).
The PCV15 vaccine is recommended for adults (19 years and older) with certain immunocompromising conditions that place them at increased risk (i.e., congenital or acquired immunodeficiency, chronic renal failure, lymphoma, generalized malignancy, solid organ transplant, anatomical or functional asplenia, sickle cell disease, etc.). A related vaccine, PPSV23, is a 23-valent pneumococcal polysaccharide vaccine introduced in 1983. A single dose is recommended for adults over 65 but should not be given simultaneously with PCV15 (they can be safely given 12 months apart with PCV15 recommended first). In certain immunocompromised individuals, this interval may be decreased to 8 weeks between vaccinations. If the PPSV23 is administered before 65, one additional dose should be administered at least five years after the previous dose. PPSV23 is also recommended for adults (19-64 years) with chronic medical conditions (i.e., chronic heart, lung, liver disease, or diabetes; alcoholism, or cigarette smoking). PPSV23 is contraindicated in those with a severe allergy, and precaution should be taken in those with moderate to severe acute illness. A single dose of PCV20 may be given in lieu of the PCV15/PPSV23 combination. PCV15 and PCV20 are contraindicated in those with a severe allergic reaction to a previous dose or a diphtheria-toxoid-containing vaccine. Precaution should be taken in those with moderate to severe acute illness. CDC, 2022a; WHO, 2021c).
For more information on pneumonia, see the Nursing CE course Pneumonia.
Hepatitis A (HepA)
Hepatitis A is a contagious virus that leads to liver infection. Transmission occurs via the fecal-oral route through close person-to-person contact, sexual contact, or ingestion of contaminated food or drink. Symptoms of a hepatitis A infection include fatigue, nausea, vomiting, abdominal pain, and the appearance of jaundice due to liver involvement. These symptoms usually appear 2-6 weeks after exposure and can last up to 6 months but do not lead to a chronic illness, and most individuals do not have long-lasting effects of the virus. Children under 6 are often asymptomatic but can transmit the disease to older children and adults who may become symptomatic (CDC, 2020d).
Currently, there is no treatment available designed explicitly for hepatitis A; therefore, the best means of protection is prevention through vaccination. There are two single-antigen HepA vaccines, Havrix and Vaqta, approved for children. These vaccines contain an inactivated form of hepatitis A. Hepatitis A vaccination is a two-dose series recommended for children ages 12-23 months old, with a second dose 6 months later. Side effects following vaccination are mild and include fever, fatigue, loss of appetite, and injection site soreness. Using vaccines, hepatitis A infections dropped by 95% from 1995 to 2011. Since 2016 there has been a spike in person-to-person transmission and infection. If a person has a functional immune system and receives both doses of any available vaccine, they are considered to have life-long immunity against hepatitis A (CDC, 2020d).
HepA is recommended in a 2- or 3-dose series for adults with additional risk factors or another indication. For adults at risk for hepatitis A or those who are not at risk but want protection, a 2-dose series of Hep A or 3-dose series of HepA-HepB can be given. Individuals considered to be at risk for hepatitis A include those with chronic liver disease, HIV infection, persons experiencing homelessness, those who work with hepatitis A in a lab, travel to countries with high rates of hepatitis A, men who have sex with men, persons who use injectable or noninjectable illicit drugs, pregnant patients, and persons who work in settings where exposure can occur such as healthcare (CDC, 2022a). For more information on hepatitis, see the Nursing CE course Hepatitis.
Hepatitis B (HepB)
HepB is a vaccination against the hepatitis B virus that attacks the liver. The WHO estimates global coverage for this vaccination at 83%, with coverage as low as 42% for newborns recommended to be vaccinated in the first 24 hours. It is currently available in 190 countries (WHO, 2021c). The HepB vaccine was approved for use in the US in 1981 (Vanderslott et al., 2019). Hepatitis B is a highly contagious disease that affects the liver. Although infected children are often asymptomatic or experience mild symptoms, they can become carriers and infect an adult who may then have more severe symptoms. Hepatitis B is transmitted through contact with infected blood or other bodily fluids and can cause lethargy, fever, decreased appetite, joint and muscle pain, abdominal pain, nausea, vomiting, and diarrhea. Hepatitis B can occur as an acute infection or develop into a chronic illness. It usually takes 3-4 months after exposure before symptoms appear (CDC, 2017).
The HepB vaccine is created using the hepatitis B surface (or ‘s’) antigen (HBsAg). The CDC recommends that children receive the hepatitis B vaccination at birth, 1-2 months old, and 6-18 months old. There are multiple hepatitis B formulations available for children. Recombivax HB and Enerix-B are single-antigen formulations (they only contain material specific to hepatitis B) and can be given as early as birth to initiate the vaccine series. It is recommended that infants receive the HepB vaccine at birth regardless of the infection status of the mother. Pediarix is a combination vaccine that contains hepatitis B, DTaP, and IPV. Pediarix is not approved for use in children under six weeks or over seven years old. HepB vaccination is administered as a three-dose series. The HepB vaccine is contraindicated in individuals that have had an allergic reaction to a previously administered HepB vaccine or have an allergy to yeast. HepB vaccination can occur concurrently with other vaccinations; however, a different site and syringe should be used. If previous vaccine administration cannot be verified, there are no contraindications to administering extra doses or restarting the entire series. A healthy individual with a functioning immune system should remain resistant to hepatitis B for approximately 30 years (CDC, 2017).
The CDC recommends 2, 3, or 4 doses for adults with specific risk factors depending on the vaccine. In addition, routine vaccination can be administered to individuals not considered at risk for hepatitis B but who want protection. Risk factors for hepatitis B include chronic liver disease, HIV infection, and sexual exposure risk (e.g., sex partners with hepatitis B, sexually active persons not in a monogamous relationship, men having sex with men, persons seeking evaluation and treatment for a sexually transmitted infection [STI]). Other risk factors include current or recent injection drug use, percutaneous or mucosal risk for exposure to blood, pregnancy, travel to countries with high hepatitis B rates, and incarceration (CDC, 2022a).
Meningitis is an infection of the meninges surrounding the brain that can be viral, bacterial, or fungal. Bacterial meningitis can be caused by Neisseria meningitidis or meningococcus. Bacterial meningitis can be severe, with a 10-15% mortality rate even with optimal treatment. It can also lead to loss of limbs, deafness, or brain damage. There is an increased risk of transmission in close living quarters, such as dormitories and barracks, as it is transmitted via saliva and other respiratory secretions. There are five main serogroups of meningococcus: A, B, C, W, and Y (Linder & Malani, 2019).
There are currently five meningococcal vaccines approved for use in the US. Three are conjugate vaccines (MenACWY-D [Menactra], MenACWY-CRM [Menveo], and MenACWY-TT [MenQuadFi]), and two are recombinant vaccines (MenB-FHbp [Trumenba] and MenB-4C [Bexsero]). The CDC recommends that the first dose of MenACWY be administered at age 11-12, with a booster dose at 16. If the first dose is administered after 16, a booster dose is not needed in healthy individuals. The MenACWY vaccine protects individuals from four different types of bacteria that cause meningococcal infections. Since the CDC began recommending the MenACWY vaccine for adolescents in 2005, the infection rate by the meningococcal serogroups included in the vaccine has decreased by more than 90% (CDC, 2021g). MenB is recommended in individuals over 10 diagnosed with complement deficiency, HIV, functional or anatomic asplenia, or are taking a complement inhibitor. Adverse effects following administration of MenACWY include irritability, malaise, headache, and injection site pain. Contraindications to vaccination include a history of anaphylactic response to a previous dose of any vaccine component (Mbaeyi et al., 2021).
The CDC recommends one or two doses of the MenACWY for adults depending on the indication. The MenACWY 2-dose series is recommended for persons with anatomical or functional asplenia or HIV infection. A single dose of MenACWY is recommended for persons traveling in countries with high rates of meningococcal disease or first-year college students living in residential housing (if not vaccinated at 16 years). The CDC recommends two or three doses of the MenB vaccine, depending on the vaccine and indication. MenB is recommended for persons with anatomical or functional asplenia and microbiologists routinely exposed to Neisseria meningitidis. In addition, persons 19-23 years at average risk may elect to receive the MenB vaccine based on a shared clinical decision between patient and provider (CDC, 2022a).
All meningitis vaccines are contraindicated in those with a prior history of severe allergic reaction to the vaccine or one of its components; precaution should be exercised before administration to those patients with a moderate to severe acute illness. Those with a prior allergic reaction to any diphtheria toxoid vaccine should not be given the MenACWY-D or CRM. Those with a prior allergic reaction to any tetanus toxoid vaccine should not be given the MenACWY-TT. Precaution should be exercised prior to administering the MenB vaccine to a patient that is pregnant or with a latex sensitivity (MenB-4C only; CDC, 2022a).
Haemophilus Influenzae Type B (Hib)
Haemophilus influenzae type b (Hib) is a bacterium that affects children under 5 years old, causing severe illness or death. Examples of infections caused by Hib include bronchitis, pneumonia, sepsis, and meningitis (CDC, 2020c). At one time, Hib was the primary cause of bacterial meningitis infections among children under 5 in the US, leading to the death of over 1,000 children each year (CDC, 2021a). The Hib vaccine is a polysaccharide conjugate vaccine that is highly effective in eliciting immunity to Hib bacteria. The vaccine is currently available in 192 countries with an estimated coverage of 70% worldwide. However, there is a significant variation in coverage: the South-East Asia region has 83% coverage, and the Western Pacific region has only 25% coverage (WHO, 2021c).
The CDC recommends that all children receive a Hib vaccination at 2, 4, and 6 months old (if using Hiberix, ActHIB, Pentacel, or Vaxelis) and a booster dose between 12-15 months old. PedvaxHIB is a three-dose series given at 2 months, 4 months, and a booster at 12-25 months. This booster dose between 12-15 months old is necessary to provide complete protection against Hib and must be given at least 8 weeks after the last dose of the Hib vaccine. Vaxelis should not be used as this booster dose. The Hib vaccine can be administered in infants as young as 6 weeks old. Hib vaccination is available as a stand-alone vaccine or in combination with other vaccinations. Hib vaccination is contraindicated in any patient with a history of severe allergic reaction to a previous Hib vaccination or any vaccine component and infants less than 6 weeks old. In patients suffering from moderate to severe illness with or without a fever, the benefits of vaccination must be weighed against the risks of vaccination. Hiberix, ActHib, and PedvaxHIB should not be given to patients with a history of severe dry natural latex allergy. The Hib vaccine is immunogenic in patients diagnosed with sickle-cell disease, leukemia, HIV, or a history of a splenectomy (CDC, 2021b).
The CDC recommends one or three doses for adults depending on the risk factors or the indication. If not previously vaccinated, one dose is recommended for patients with anatomical or functional asplenia, including sickle cell disease. In addition, one dose is recommended at least 14 days before surgery if undergoing elective splenectomy. Finally, a three-dose series is recommended for patients undergoing hematopoietic stem cell transplant (HSCT) regardless of vaccination history. The three-dose series should be given four weeks apart, beginning 6 to 12 months after transplantation. As mentioned above, Hib is contraindicated in any adult with a prior severe allergic reaction to the vaccine or one of its components, and precaution should be taken before administering to a patient with moderate to severe acute illness (CDC, 2022a).
At one time, polio was the most feared disease in the US, causing disability in over 35,000 people per year in the US. Parents were afraid to send their children out of the house, and government-imposed quarantines were implemented to prevent the spread of the poliovirus. Unlike other viruses, the rate of infection increased over the summer months. In 1955 the first vaccine designed against polio was introduced. The length of immunity is unknown; however, the poliovirus has been eliminated from the US. There have not been any cases of poliovirus that originated in the US since 1979 (Estivariz et al., 2021). However, there is still a risk of exposure for those traveling internationally to areas where the poliovirus is still a threat, such as Pakistan, Afghanistan, or Nigeria (Shah et al., 2016).
The CDC recommends administering four doses of IPV at 2, 4, 6-18 months, and 4-6 years old. If a child received IPV in a combination vaccination, they might require a fifth dose, which is safe and recommended. Once three doses are administered, the protection rate against polio is 99-100%, and at four doses, a child is considered fully vaccinated. There is an accelerated vaccination schedule for children traveling outside of the US to an area where the risk of contracting polio is increased. If the accelerated schedule cannot be completed prior to departure, the series should be continued upon arrival to the destination or immediately upon return to the US. If a child is vaccinated outside of the US and cannot provide reliable vaccination documentation, they should be vaccinated following the CDC vaccination schedule (CDC, 2018a).
IPV is contraindicated in individuals that have a history of allergic reaction to a previous dose of IPV vaccine and any components of the vaccine, including streptomycin, polymyxin B, and neomycin, or are suffering from a moderate to severe illness. Common adverse effects include localized pain and erythema, fever, irritability or fussiness, fatigue, and crying. Adverse effects following IPV administration tend to be mild with a short duration. The IPV vaccine needs to be refrigerated when not in use at 36-46° F (2-8° C, Estivariz, et al., 2021).
Rotavirus causes a viral illness characterized by severe diarrhea, vomiting, fever, and abdominal pain in infants and young children. Rotavirus is transmitted via the stool of an infected individual. Rotavirus can survive on the surface of inanimate objects for several days and is difficult to prevent through good hand hygiene and surface cleaning, leading to a quick spread through families, hospitals, and childcare centers. The effects of rotavirus can last for 3-8 days, and children may not tolerate oral intake during active infection. Rotavirus infection can be critical, especially in infants and young children, due to diarrhea, fever, and vomiting coupled with a lack of oral intake. This combination can cause severe dehydration, which can be life-threatening and may require hospitalization for fluid resuscitation via intravenous fluid replacement. Diarrhea is responsible for 1 in 9 pediatric deaths worldwide, resulting in over 2,000 deaths daily (CDC, 2021m).
It is recommended that children are vaccinated against rotavirus to prevent infection and serious complications (CDC, 2021i). The rotavirus vaccine was approved for use in the US in 2006 (Vanderslott et al., 2019). Currently, two rotavirus vaccines are approved for use: RotaTeq and Rotarix. Both vaccines contain live-attenuated forms of rotavirus and are given orally. The primary difference is that RotaTeq requires three doses, and Rotarix only requires two doses to be considered fully vaccinated. Administration of RotaTeq should occur at 2, 4, and 6 months of age. Administration of Rotarix should occur at 2 and 4 months of age. The first dose of either vaccine should be administered before 15 weeks of age, and the entire series should be administered before 8 months old. If the first dose is administered to an infant older than 15 weeks, the remaining doses should be administered according to the recommended schedule. Children over 8 months should not receive the rotavirus vaccine even if the series has not been completed (CDC, 2021i).
Both vaccines typically cause only mild adverse effects such as irritability, mild diarrhea, and vomiting. In rare cases, intussusception may occur, requiring hospitalization and possibly surgery. If intussusception were to occur, it usually occurs within one week of administration. The rotavirus vaccine is contraindicated in infants with a history of allergic reaction to a previous dose of the vaccine or any component of the vaccine, intussusception, or severe combined immunodeficiency. Infants that are mildly ill may still receive the rotavirus vaccine, but any moderately or severely ill infant should wait until they recover to receive the vaccine. This includes any infant suffering from moderate to severe diarrhea or vomiting (CDC, 2021i).
Two vaccines are often recommended for pregnant women: influenza and Tdap. A recent study looking at over 60,000 children born to women who received the influenza vaccine during pregnancy found no increased risk of early childhood morbidity (up to the age of 4-5; Hviid et al., 2017). In addition, Zerbo et al. (2017) looked at almost 200,000 children in northern California born between 2000 and 2010. They found no increased risk for autism spectrum disorders (ASD) in children born to mothers with influenza infections or who received the influenza vaccine during pregnancy. When the risk was broken down by trimester, only when the mother was vaccinated during the first trimester was there a slight increase in risk (Zerbo et al., 2017). The CDC recommends IIV or RIV for pregnant women, as live vaccinations (i.e., LAIV) are not recommended in pregnancy. One dose of the Tdap vaccine is recommended in pregnancy, preferably in weeks 27 to 36 (CDC, 2022a).
Other vaccinations, such as the HPV vaccine, may occur inadvertently when the woman is not yet aware that she is pregnant. For example, a study in Denmark reviewed over 1,600 pregnancies exposed to the HPV vaccine. The researchers found no significantly increased rates of significant congenital disabilities in exposed versus unexposed pregnancies (3.9% versus 3.3%), spontaneous abortion (4.3% versus 7%), preterm delivery (6.5% versus 5.7%), low birth weight (4.3% versus 3.9%), small for gestational age (9.7% versus 11%) or stillbirth (0.4% versus .2%; Scheller et al., 2017). Therefore, the CDC recommends that the HPV vaccine not be given until after pregnancy; however, no intervention is required if the person is vaccinated while pregnant. The CDC recommends that the HepA and Hep B vaccines be administered during pregnancy if the person is at risk of infection, although Heplisav-B is contraindicated in pregnancy. The MMR vaccine is a live vaccine and is, therefore, contraindicated during pregnancy but can be given after delivery before discharge. Similarly, the VAR vaccine is contraindicated during pregnancy but can be administered after delivery before discharge. The CDC recommends delaying administration until after pregnancy for the meningitis vaccine unless the benefits outweigh the potential risks. RZV should also be postponed until after pregnancy (CDC, 2022a).
Global Vaccination Trends
Some diseases are found more frequently outside of the US and represent a significant risk to worldwide health, such as dengue fever, malaria, and cholera. Dengue fever (or dengue) is a mosquito-borne illness caused by the dengue virus. Up to 20% of the severe form of dengue is lethal. It is mainly found in very rainy areas/seasons of Bangladesh and India, but roughly 40% of the world is at risk, with 390 million cases worldwide annually. The vaccine developed for dengue by Sanofi is a live attenuated vaccine called CYD-TDV or Dengvaxia. It was released in 2015 and is currently approved in 20 endemic countries for individuals ages 9-45. While the vaccine is helpful, it is far from a perfect solution. While the vaccine improves immunity in patients with a prior history of dengue infection (seropositive), it increases the risk of severe dengue and hospitalizations in seronegative people. For that reason, people must have a confirmed history of dengue infection or should be screened with an antibody titer prior to vaccination. For this reason, most prevention programs currently focus on reducing transmission via the mosquito Aedes aegypti (WHO, 2019a, 2022).
Malaria is a parasitic infection transmitted by Anopheles mosquitoes. Five parasite species cause malaria, with P. falciparum and P. vivax posing the greatest risk. Worldwide, there were 241 million malaria cases in 2020, with 627,000 associated deaths. The African region accounted for 95% of malaria cases and 96% of malaria deaths. In addition, children under 5 years old accounted for 80% of all malaria deaths in that region. RTS,S/AS01 (Mosquirix) is an injectable vaccine that has been shown to significantly reduce malaria and severe malaria among children. Therefore, since October 2021, the WHO has recommended the general use of the RTS,S/AS01 malaria vaccine for children living in moderate to high transmission regions. An ongoing pilot program of the RTS,S vaccine in Ghana, Kenya, and Malawi has reached more than 800,000 children since 2019 (WHO, 2021a; 2021d).
Cholera causes acute diarrhea, and 80% of cases can be treated effectively with oral rehydration. There are currently three oral vaccines available to prevent cholera. Dukoral is approved for use in children over the age of 2, with three doses recommended in age 2 to 5 or two doses for adults or children over 5. Dukoral protects for two years and can be used for people traveling to areas with a higher risk of cholera. Shanchol and Euvichol-Plus are both approved for use in adults and children over 12-months-old; both vaccines consist of two doses and protect for three years (WHO, 2021b). The practical use of Shanchol was tested recently in a group of patients in Bangladesh. A single dose of the vaccine was shown to have an efficacy rate of 40% against all cholera episodes and 63% against severe cholera episodes. It was most efficacious in children 5-14 years old. A limitation of this study was its short follow-up, which was only 180 days (Qadri et al., 2016).
The WHO listed vaccine hesitancy as one of the top ten threats to global health in 2019. They define vaccine hesitancy as reluctance or refusal to vaccinate despite the availability of vaccines. According to the WHO, this hesitancy has led to a 30% increase in measles cases worldwide. This movement against vaccinating children has been dubbed the Antivaxxer Movement. The most common reasons cited for vaccine hesitancy include complacency, inconvenience in access, and lack of confidence in vaccine efficacy and safety (WHO, 2019b). A recent study on the public health and economic consequences of vaccine hesitancy predicted that a 5% decrease in MMR vaccine coverage in the US would lead to three times the number of annual measles cases in children between 2 and 11. This would correlate with over $2 million in public sector costs. These figures would not include costs and cases amongst infants, adolescents, and adults. The researchers cited that the most common reasons to refuse or delay vaccination are misinformation related to safety and a reduced perceived risk of the disease itself (Lo & Hotez, 2017).
Even though the US achieved the elimination of endemic measles in 2000, there have been several measles outbreaks in the last ten years in the US related to unvaccinated individuals. For example, 383 cases were reported in and around an Amish community in Ohio in 2014. In 2014-15, an outbreak at Disneyland in California led to 147 cases being reported. In 2017, 75 cases were reported in and around a Somali-American community in Minnesota. In 2018, there were 282 cases reported in and around an Orthodox Jewish community in New Jersey and New York. It can cost up to $142,000 to respond to a single case of measles. Measles is dangerous during the active infection and causes post-infection immunosuppression that increases all-cause mortality for 2-3 years following the primary infection secondary to resetting previously acquired immunity, a phenomenon known as immunological amnesia. Outbreaks also strain public health and healthcare systems, diverting human and other resources away from other critical ongoing projects (Sundaram et al., 2019).
In an attempt to increase vaccination rates, California passed SB277 in 2016, eliminating the personal belief exemption (PBE). This move meant that any child entering a public or private kindergarten in the fall of 2016 would have to be vaccinated or obtain a medical exemption (ME). PBEs decreased in the 2016-17 school year from 2.37% to 0.56% (due to grandfathering in some students already enrolled in multiyear transitional kindergarten programs), the lowest since 1996. To obtain an ME, a child must receive a note from their primary care provider (PCP), which includes the medical reason why the child cannot be vaccinated. There is slightly broader discretion to obtain an ME, which now includes family medical history as a potential reason. The number of MEs increased from 0.17% to 0.51% in the 2016-17 school year, but the total exemptions from both sources decreased from 2.54% to 1.06%, the lowest since 2000 (Delamater et al., 2017). Vaccination hesitancy has become even more prominent due to the COVID-19 pandemic. When the COVID-19 vaccines became available, their safety and effectiveness were globally debated. The CDC reports various myths related to the COVID-19 vaccines, including:
- the ingredients in the vaccine are dangerous
- natural immunity is better than immunity from the vaccine
- the vaccine causes variants
- all events reported to the Vaccine Adverse Event Reporting System (VAERS) are caused by the vaccine
- the mRNA vaccine is not considered a vaccine
- the vaccine contains microchips
- the vaccine can alter DNA
- the vaccine can cause COVID-19 (CDC, 2021h)
Vaccine hesitancy has been so prominent with the COVID-19 pandemic that the CDC has created a strategic framework known as Vaccinate with Confidence. This strategic plan aims to strengthen vaccine confidence and prevent outbreaks of vaccine-preventable diseases in the US. Resources can be found on the CDC website (2021l). For more information on the COVID-19 vaccine, see the Nursing CE course COVID-19 Vaccine Education.
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