INTRODUCTION — This topic reviews the reasons why some parents refuse or are hesitant to have their child(ren) immunized, the consequences of vaccine refusal, and an approach to the management of parents who refuse vaccines for their children. Standard childhood immunizations for children are discussed separately. (See "Standard immunizations for children and adolescents: Overview".)
DEFINITION — According to the World Health Organization Strategic Advisory Group of Experts Working Group on Vaccine Hesitancy [1]:
●Vaccine hesitancy refers to "a delay in acceptance or refusal of vaccination despite availability of vaccination services. Vaccine hesitancy is complex and context specific, varying across time, place, and vaccines. It is influenced by factors such as complacency, convenience, and confidence."
•Complacency refers to the perception that the risks of vaccine-preventable diseases are low.
•Convenience refers to the availability, affordability, and accessibility of vaccines.
•Confidence refers to trust in the safety and effectiveness of vaccines, the health care system, and policymakers who recommend vaccines.
STATE LAWS REGARDING VACCINATION — Laws that require immunization for school entry are associated with increased rates of immunization and decreased rates of vaccine-preventable diseases [2].
Every state in the United States requires some immunizations for school entry (typically for kindergarten, seventh grade, and college entry). However, parents can elect to exempt their children from immunizations for three reasons:
●Medical exemptions – For children with a valid medical contraindication to a vaccine or vaccine component (eg, history of anaphylaxis to a previous dose of vaccine)
●Religious exemptions – For individuals whose religious beliefs oppose immunizations
●Philosophical exemptions – For individuals with a personal, moral, or philosophical belief against some or all immunizations
All states allow medical exemptions; nearly all states allow exemptions based upon religious beliefs, and approximately one-third allow philosophical exemptions [3]. The National Conference of State Legislatures and the Immunization Action Coalition provide a comprehensive list of state exemption statutes. The American Academy of Pediatrics (AAP) provides an interactive map that provides state-by-state information about nonmedical exemptions. Although the majority of proposed vaccine legislation between 2011 and 2017 aimed to expand vaccine exemptions, bills that limited vaccine exemptions were more likely to be enacted into law [4]. Proposed legislation to limit vaccine exemptions increases when vaccine-preventable diseases increase in a community [5].
The ease with which exemptions can be obtained affects exemption rates within communities [6-9]. States that allow philosophical and religious exemptions have higher exemption rates than those with religious exemptions only [10-12]. They also have higher rates of vaccine-preventable diseases [13-17]. When states eliminate philosophical exemptions, religious exemptions appear to increase [18]. (See 'Consequences of vaccine refusal' below.)
The AAP [19], the Pediatric Infectious Diseases Society [20], the Infectious Diseases Society of America [21], the American Academy of Family Physicians [22], and the American Medical Association [23] support elimination of nonmedical exemptions to immunizations.
Legislation that eliminates nonmedical exemptions is strengthened by requiring a standardized review of medical exemptions to ensure that they are valid. After California passed legislation eliminating nonmedical exemptions that was not accompanied by standardized review of medical exemptions, there was an increase in medical exemption claims that were not true contraindications to immunization [24,25].
EPIDEMIOLOGY
●Prevalence – The proportion of children who are exempted from school immunization requirements for nonmedical reasons is the primary measure of vaccine refusal in the United States [26]. The rate of nonmedical exemptions at kindergarten entry varies geographically among states; for the 2018-2019 school year, it ranged from 0.7 to 7.4 percent among states that allow religious or philosophic exemptions; the median rate of nonmedical exemptions was slightly increased from 2017-2018 (2.5 versus 2 percent) [27,28]. Individual states may have even greater within-state variation [29]. State-specific vaccine exemption information is available from the American Academy of Pediatrics.
Vaccine hesitancy is a concern worldwide [30]. A recurring survey that analyzes attitudes towards vaccine safety, effectiveness, importance, and religious compatibility found wide variability between world regions and countries and, within countries, changes in vaccine attitudes over time [31-33]. Although worldwide attitudes were overall positive, attitudes towards vaccine safety were more negative in Europe, with 41 percent of respondents in France and 36 percent in Bosnia and Herzegovina disagreeing that vaccines are safe. An analysis of the World Health Organization/United Nations Children's Fund Joint Report Form through June 2017 confirmed that vaccine hesitancy is present in the majority of countries globally and increased annually between 2014 and 2016 [34].
Although the overall prevalence of complete vaccine refusal remains low (approximately 1 percent of United States children <3 years of age [35]), substantial numbers of parents refuse one or more vaccines or request that they be administered on an alternative schedule (eg, limiting the number of vaccines per visit or omitting a particular vaccine altogether) [26,36-41]. Many parents have concerns about vaccines, even if they ultimately choose to vaccinate their children [37,42,43]. In a nationwide online survey, 6 percent of parents reported hesitancy about routine childhood vaccines and 25 percent reported hesitancy about influenza vaccines [44]. Undervaccination is more common in children with autism spectrum disorder (ASD) and their younger siblings than in children without ASD and their younger siblings [45].
●Vaccine beliefs – Scientific characterization of parents according to vaccine beliefs is difficult. Surveys and interviews have identified a spectrum of parental attitudes and beliefs about vaccines, ranging from "immunization advocate" to "immunization refuser," depending upon how strongly they agree or disagree that vaccines are necessary and safe [46-49].
Approximately 50 to 60 percent of parents agree or strongly agree that vaccines are necessary and safe. Approximately 40 percent have concerns about necessity or safety; this group may vaccinate their children despite their concerns or may choose to delay or refuse one or more vaccines.
Parents who seek vaccine exemptions may have a low level of trust in the government and health care professionals and may use complementary or alternative medicine professionals whom they consider to be reliable sources of vaccine information [50,51]. They also may refuse other medical interventions (eg, neonatal vitamin K) [52].
WHY PARENTS REFUSE VACCINES
General objections — Concerns about safety and side effects account for approximately 60 to 70 percent of vaccine exemption requests [50,53,54].
Safety concerns include specific side effects (eg, Guillain-Barré syndrome, intussusception, pain) and more general concerns (eg, that too many vaccines overload the immune system, possibly causing autism, autoimmune disease, or increased susceptibility to infection) [50,55-58]. Concerns about safety are intensified by negative word of mouth and media messages [54,58-60].
Some safety concerns have a factual basis (eg, rotavirus vaccine and intussusception), whereas others are misconceptions (eg, that multiple vaccines overwhelm the immune system) [61,62]. (See "Rotavirus vaccines for infants", section on 'Intussusception'.)
Other parental objections may be related to the belief that vaccines are not necessary or the lack of choice. Examples include [37,40,50,54,58,60,63-68]:
●Belief that vaccines do not work
●Belief that their child is not at risk or that the vaccine-preventable disease is not dangerous
These beliefs are a consequence of the success of childhood immunization programs (figure 1). As more diseases are successfully prevented by immunization, parents have little familiarity with the devastating effects of vaccine-preventable diseases [69]. They may be unaware of the risks to their child and the community at large if they refuse vaccines. For parents who are unfamiliar with vaccine-preventable diseases, potential adverse effects may seem more important than potential benefits. (See 'Consequences of vaccine refusal' below.)
●Belief that it is better to be naturally infected than vaccinated
●Belief that parents know what is best for their child and should have the right to make decisions for them
●Lack of trust in government health authorities, organized medicine, public health officials, and/or pharmaceutical companies
●Ethical, moral, or religious objections (eg, immunizations are a violation of God's will)
Specific objections — Parents (and providers) may have a tendency to selectively protect against diseases they believe are more severe (eg, Haemophilus influenzae type b) and refuse vaccines against diseases that they believe are not dangerous (eg, varicella) [26].
MMR vaccine — The major concern about the combination measles-mumps-rubella (MMR) vaccine, which is unfounded, is that MMR causes autism. This concern can be traced to a 1998 study in 12 children alleging that MMR damaged the intestinal lining, allowing encephalopathic proteins to enter the bloodstream and brain, thereby leading to the development of autism [70]. The paper was retracted from the public record in 2010 and exposed as fraudulent in 2011 [71-76]. Despite overwhelming evidence disproving this theory, it still is highlighted in media reports and on the internet [77]. The absence of a causal association between MMR vaccine and autism is discussed separately. (See "Autism spectrum disorder and chronic disease: No evidence for vaccines or thimerosal as a contributing factor", section on 'MMR vaccine and ASD'.)
Another concern related to MMR vaccine, which is also unfounded, is the belief that measles vaccine should be avoided because measles infection protects against cancer [78]. Although there is evidence that oncolytic measles virotherapy (ie, using engineered measles virus to treat cancer) may be helpful, evidence that wild-type measles virus prevents cancer is lacking [78-81]. In addition, studies of oncolytic measles virotherapy suggest that vaccination against measles will increase rather than decrease the potential benefits [78].
HPV vaccine — Concerns regarding the human papillomavirus (HPV) vaccine are related to the erroneous belief that it may encourage sexual activity [82,83], belief that it is unnecessary [84], perceived excessive influence by the pharmaceutical industry [85,86], and misinformation regarding its safety [57,67,87,88], including the mistaken belief that it caused the death of a girl whose autopsy demonstrated that she died of an undiagnosed tumor [89].
The media focus on these concerns may have contributed to the number of adverse events reported to the Vaccine Adverse Event Reporting System (VAERS) between June 2006 and December 2008 [90,91]. However, analysis of postlicensure VAERS reports indicates that adverse events were similar to those identified in prelicensure trials [91]. In addition, the rates of adverse events were similar to background rates of other vaccine-associated adverse events, except for syncope, which is more common in the age-group for which HPV vaccine is recommended [92]. Other adverse events that appeared to be vaccine-related have not been substantiated.
The safety of HPV vaccine is discussed separately. (See "Human papillomavirus vaccination", section on 'Vaccine safety'.)
Meningococcal conjugate vaccine — The major concern about the quadrivalent meningococcal conjugate vaccine is a possible association with Guillain-Barré syndrome [93]. Although Guillain-Barré syndrome has been temporally associated with vaccination, a causal association has not been proven. (See "Meningococcal vaccination in children and adults", section on 'Adverse events'.)
Influenza — Parental concerns about influenza vaccines include Guillain-Barré syndrome, thimerosal exposure, inadequate testing to ensure safety in children, and belief that there is no need for protection against what may be mistakenly considered a "mild type" of influenza [94], a belief strengthened by the false characterization of other respiratory viral illnesses as influenza or "flu."
Concerns about influenza vaccine-associated Guillain-Barré syndrome and other neurologic complications were highlighted by the media during the 2009 H1N1 influenza pandemic. Some commentators erroneously compared the rapid development of monovalent pandemic H1N1 influenza vaccines to the effort for rapid development of a swine flu vaccine in 1976, which was associated with Guillain-Barré syndrome.
However, monovalent H1N1 vaccine was developed using the same methods that are used for seasonal influenza vaccine, and the increased risk of Guillain-Barré syndrome following seasonal influenza vaccine was found to be small or nonexistent [95-97]. (See "Seasonal influenza in children: Prevention with vaccines", section on 'Adverse effects' and "Guillain-Barré syndrome in adults: Pathogenesis, clinical features, and diagnosis", section on 'Vaccinations'.)
Thimerosal has been hypothesized to result in mercury-related neurologic effects, including the development of autism. Numerous studies refute this hypothesis, but some parents remain unconvinced. Thimerosal-free preparations of influenza vaccine are available for families who remain concerned about thimerosal exposure. (See "Seasonal influenza in children: Prevention with vaccines", section on 'Types of vaccine' and "Autism spectrum disorder and chronic disease: No evidence for vaccines or thimerosal as a contributing factor".)
Aluminum adjuvants — Aluminum is used as an adjuvant in many inactivated vaccines (eg, hepatitis B vaccine, diphtheria-tetanus-acellular pertussis vaccine, pneumococcal conjugate vaccine). Aluminum adjuvants are considered to be both safe and effective, with rare adverse effects [98,99]. There has been concern that the cumulative dose of aluminum from childhood vaccines exceeds safe levels [100]. However, during the first year of life, the total body burden of aluminum from diet and vaccines is lower than the minimal risk level determined by the Agency for Toxic Substances and Disease Registry [100,101]. In a cross-sectional study of children age 9 to 13 months, no correlation was found between blood and hair aluminum levels and immunization history [102].
Although aluminum has been hypothesized to play a role in the development of autoimmune diseases (eg, macrophagic myofasciitis, autoimmune autoinflammatory syndrome induced by adjuvants) [103-105], evidence does not support the hypothesis [57,106-109]. In a population-based study, the risk of autoimmune disease was lower among patients who received aluminum-containing allergen-specific immunotherapy (which contains more aluminum than vaccines) than among patients receiving conventional allergy treatment [110].
CONSEQUENCES OF VACCINE REFUSAL
For the individual — Vaccine refusal increases the risk of vaccine-preventable diseases among unvaccinated individuals [111].
●Risks of vaccine refusal – Unvaccinated children have a greater risk of acquiring vaccine-preventable disease than their vaccinated peers. In observational studies and mathematical modeling, the magnitude of the increased risk is approximately nine-fold for varicella, as high as 35-fold for measles, and ranges from 6- to 28-fold for pertussis [112-117].
A systematic review evaluated the association between vaccine refusal and measles infection in the United States between 2015 and 2020 [17]. Among the 1392 people with measles, 71 percent had no history of measles vaccination, 11 percent had a history of measles vaccination, and 18 percent had unknown vaccination status. Although the reason for lack of vaccination (eg, medical exemption, religious exemption) was not consistently documented, 82 percent of those who were unvaccinated were old enough to have received a measles vaccine.
●Risks of vaccine delay – The risks of delaying immunization have not been well studied [26]. As a general rule, vaccine-preventable diseases (eg, pertussis, influenza) are more severe in infants and young children than in older children. Delaying immunizations increases the duration of vulnerability for these young children.
For the community — Vaccine refusal increases the risk of outbreaks of vaccine-preventable diseases in the general population [111,118]. The World Health Organization considers vaccine hesitancy a threat to global health [119]. In addition to causing preventable illness in the community, outbreaks of vaccine-preventable diseases unnecessarily consume public health resources (eg, for laboratory testing, contact investigation, control measures) [120-122].
In observational studies, unvaccinated individuals tend to cluster geographically, making some communities more vulnerable [6,14,120,123-126].
These outbreaks may affect individuals who are unvaccinated due to religious or philosophical objections to vaccines, children too young to be vaccinated, people with contraindications to vaccines, and vaccinated individuals with suboptimal immune response or waning immunity [114,120,127,128]. The rates of disease among vaccinated individuals increase as vaccinated and unvaccinated individuals mix in communities [14,16,114,115].
Multiple outbreaks of vaccine-preventable diseases (measles, polio, rubella, pertussis, H. influenzae type b) have been related to religious groups or communities opposed to immunization [120,122,125,128-137]. In 2019, the United States experienced the highest number of measles cases since the United States was declared measles free in 2000 [138,139]. The Centers for Disease Control and Prevention provides information about measles outbreaks in the United States and around the world.
APPROACH TO MANAGEMENT — Our approach to the management of vaccine hesitancy involves establishing a positive dialogue, identifying parental concerns, providing education targeted to those concerns, maintaining a relationship with the family, and making every effort to follow the recommended immunization schedule, as described in the sections below. Our approach is consistent with that of the American Academy of Pediatrics (AAP) Committees on Infectious Diseases, Practice and Ambulatory Medicine, and Bioethics [68,140,141].
A 2015 systematic review of strategies for addressing vaccine hesitancy found few strategies explicitly designed to address vaccine hesitancy or to quantify the impact of the intervention and wide variation in effect size, settings, and target populations [142]. However, multicomponent and dialogue-based interventions appeared to be most effective. Previsit screening for vaccine hesitancy has not been shown to improve on-time immunization [143].
Establish a positive dialogue — Establishing a positive, nonconfrontational dialogue that presumes that the parents will ultimately vaccinate the child is essential to ensuring a successful outcome [68,144]. The dialogue should begin at the first provider-parent encounter and continue at every subsequent interaction. Having the dialogue and establishing/maintaining trust is more important than the outcome at any one visit [145]. The goals are to identify specific parental concerns and the forces that influence the parents' knowledge and attitudes toward vaccines [146,147].
Key points in establishing the dialogue include [68,145,148]:
●Acknowledging a shared goal (ie, what is best for the child)
●Acknowledging the large volume of complex, conflicting information about vaccine benefits and safety
●Offering to help parents to gather and interpret the best information to make an informed decision (table 1)
The health care provider has an important influence on decisions about immunization, even among vaccine-hesitant parents [65,66,149-151]. Surveys suggest that approximately one-third to one-half of vaccine-hesitant parents eventually vaccinate their children [42,63,144,152]. The ability to persuade vaccine-hesitant parents to immunize their children may be related to the source and strength of their concerns [153].
How the provider initiates the conversation about vaccines may play a role in vaccine acceptance. In observational studies, a presumptive approach (eg, "He is due for three shots today") was associated with less parental resistance to immunizations than a participatory approach (eg, "What would you like to do about shots?") [144,154,155]. However, the presumptive approach was also associated with lower ratings for visit experience, suggesting that further study is needed to determine the optimal use of this approach.
Additional information about communicating with vaccine-hesitant parents and sample scripts are available through the AAP, the World Health Organization (WHO), the Autism Science Foundation, and in reference [47] (free full text available through BioMed Central).
Identify concerns — A major goal of the dialogue is to identify parental concerns and the forces that influence parental concerns about vaccines (eg, family members, religious community, the media, etc). Alternatively, some parents may hold strong beliefs in conspiracy theories, suffer extreme fear of or aversion to medical interventions, or prefer to take an individualist or nonconformist approach to medical recommendations [156]. Regardless of the source of vaccine concerns, providers may inadvertently make incorrect assumptions about parental attitudes and beliefs (eg, mistaking lack of knowledge for hesitancy or overestimating the strength of parental beliefs) [146,147]. Once the concerns are identified, the provider can establish a plan for targeted education to address them. (See 'Why parents refuse vaccines' above and 'Target education' below.)
Some concerns may not be immediately obvious. Parents who are concerned that their infant may suffer during vaccine administration may fear committing harm (eg, giving an unsafe vaccine) more than permitting harm (eg, taking a chance that their child will develop a disease) [148]. Providers must listen carefully and respectfully to understand these concerns, even if it is time consuming.
Respectful listening is also critical to identifying the source of parental concerns. Parents may receive vaccine information from mainstream media or the internet [58]. The mainstream media has a limited ability to adequately communicate scientific information about vaccines, and internet sites are not subject to constraints regarding scientific accuracy or the fairness of their reporting.
Mainstream media reports are designed to gain attention, present information that is easy to understand, and highlight pro- and antivaccine viewpoints in a limited span of time. They may give equal or greater weight to ill-informed opinions or anecdotal claims about the dangers of vaccines than to the rigorous scientific studies that prove vaccines are safe and effective [59,69,77,157]. Erroneous impressions from the media (including social media) may be reinforced by stories from family members, friends, or the internet [54,58,158,159]. The resulting misinformation leads to unnecessary parental concerns. Health care providers need to understand these concerns in order to effectively address them.
Target education — Many parental concerns about vaccines are amenable to dialogue and discussion. The provider must address relevant concerns while emphasizing that vaccines are safe and effective and that serious disease can occur if the child and family are not vaccinated, realizing that some parents may need information from a variety of resources (table 1) [68].
Providers should target education to specific parental concerns and/or beliefs. Potential topics include:
●Vaccine benefits and limitations
●Vaccine safety and adverse events
●Risks of natural infection
●Correcting misconceptions
●Injection pain
Strategies for each of these targets are discussed below.
Vaccine benefits and limitations — Immunization is one of the most effective preventive health measures (figure 1) [160]. In 2014, the Centers for Disease Control and Prevention (CDC) estimated that, among children born from 1994 through 2013, vaccination would prevent 322 million illnesses, 21 million hospitalizations, and 732,000 deaths [161].
However, it is important to acknowledge the limitations of vaccines: They are neither 100 percent effective nor are they completely risk free. Although provision of this information helps to establish credibility, it must be placed in proper context, particularly for parents who tend to overestimate the risks of vaccines and underestimate the risks from vaccine-preventable diseases [69]. For such parents, it may be helpful to define the options in terms of benefits with risks, rather than focusing on risks alone [61].
Vaccine safety and adverse events — Vaccines that are recommended for children in the United States are fully tested in large numbers of subjects before they are licensed by the US Food and Drug Administration (FDA) [68,162]. After they are licensed, they are monitored by the CDC and the FDA through the Vaccine Adverse Event Reporting System and the Vaccine Safety Datalink. When concerns are identified, the FDA issues news releases and may temporarily or permanently suspend the use of a specific vaccine (eg, the RotaShield rotavirus vaccine was withdrawn from the market in 1999) [163]. (See "Rotavirus vaccines for infants", section on 'Intussusception'.)
Most vaccine-associated adverse events are minor and self-limited (eg, local skin reactions, transient low-grade fever). Serious adverse events are rare and should be discussed in the context of the risks associated with natural infection [164]. As examples:
●The risk of acquiring measles during an outbreak may be 35 times higher in an unvaccinated than in a vaccinated person [115].
●The risk of measles-associated encephalopathy or subacute sclerosing panencephalitis following natural measles is much higher than the risk of encephalopathy from measles vaccine. (See "Measles: Clinical manifestations, diagnosis, treatment, and prevention", section on 'Subacute sclerosing panencephalitis'.)
Risks of natural infection — For vaccine-hesitant parents who lack accurate information or have misconceptions about vaccine safety, focusing only on correcting misconceptions may lead to a paradoxical strengthening of mistaken beliefs, a phenomenon known as confirmation bias. In this situation, it may be helpful and more effective to highlight factual information about the risks and complications of natural infection with vaccine-preventable diseases [165].
In the context of provider-parent discussion, visual imagery and anecdotes from parents who are vaccine advocates, and with whom other parents can identify, may be used to support the educational message that serious disease can occur if the child and family are not immunized [68]. Without the associated discussion, preferably with a trusted provider, these educational messages may not have the intended effect (ie, increased vaccination), particularly among parents with the least favorable view of vaccines [166]. Visual imagery and anecdotes from parents who are vaccine advocates are available from Families Fighting Flu, Meningitis Angels, National Meningitis Association, and Vaccine-preventable disease: The forgotten story.
The potentially serious consequences of vaccine-preventable diseases are discussed separately:
●Hepatitis B (see "Clinical manifestations and diagnosis of hepatitis B virus infection in children and adolescents", section on 'Hepatocellular carcinoma')
●Diphtheria (see "Clinical manifestations, diagnosis, and treatment of diphtheria", section on 'Clinical manifestations')
●Tetanus (see "Tetanus", section on 'Clinical features')
●Pertussis (see "Pertussis infection in infants and children: Clinical features and diagnosis", section on 'Clinical features' and "Pertussis infection in adolescents and adults: Clinical manifestations and diagnosis", section on 'Complications')
●Polio (see "Poliomyelitis and post-polio syndrome", section on 'Clinical features')
●H. influenzae type b and Streptococcus pneumoniae (see "Bacterial meningitis in children older than one month: Clinical features and diagnosis", section on 'Clinical features' and "Community-acquired pneumonia in children: Clinical features and diagnosis", section on 'Complications' and "Epiglottitis (supraglottitis): Clinical features and diagnosis", section on 'Clinical presentation')
●Rotavirus (see "Clinical manifestations and diagnosis of rotavirus infection", section on 'Clinical manifestations')
●Influenza (see "Seasonal influenza in children: Clinical features and diagnosis", section on 'Complications')
●Measles (see "Measles: Clinical manifestations, diagnosis, treatment, and prevention", section on 'Complications')
●Mumps (see "Mumps", section on 'Complications')
●Rubella (see "Rubella", section on 'Clinical manifestations')
●Varicella (see "Clinical features of varicella-zoster virus infection: Chickenpox", section on 'Complications of varicella')
●Hepatitis A (see "Overview of hepatitis A virus infection in children", section on 'Clinical manifestations')
●Human papillomavirus (see "Virology of human papillomavirus infections and the link to cancer", section on 'HPV Genotypes and risk of cancer' and "Epidemiology, staging, and clinical presentation of human papillomavirus associated head and neck cancer")
●Meningococcal disease (see "Clinical manifestations of meningococcal infection", section on 'Meningitis and acute meningococcemia')
Misconceptions — It is important to dispel myths, correct misinformation, and direct parents to scientifically sound information (table 1) [61,68,167]. Providers should avoid using ambiguous language or complicated scientific terms when discussing the evidence supporting vaccine safety and effectiveness. The WHO suggests that providers emphasize core facts, keep the message simple, make explicit warnings, explain why the myth is wrong, use graphics (eg, to demonstrate the number of children who will develop measles if they are vaccinated compared with if they are not vaccinated), and avoid strong language (which can paradoxically increase the perception of risk) [168,169].
●Autism – The most common vaccine myth is that vaccines, particularly the combined measles-mumps-rubella vaccine and thimerosal-containing vaccines, cause autism. These myths are discussed separately. (See "Autism spectrum disorder and chronic disease: No evidence for vaccines or thimerosal as a contributing factor".)
●Multiple vaccines overwhelm the immune system – Parents may worry that receiving multiple vaccines on the same day overwhelms the immune system, possibly causing autism, autoimmune disease, or increased susceptibility to infections.
The following information may help to dispel this misconception [57,62,170-172]:
•With manufacturing advances and the discontinuation of smallpox immunization, children younger than two years are exposed to fewer antigens than they were in 1980 (approximately 125 versus >3000) [173-175]. It may be necessary to explain the difference between an antigen and a vaccine or shot. For parents who struggle to understand the difference between an antigen and a vaccine, providers can explain that an antigen is a tiny piece of a germ. A vaccine contains either a group of antigens from a killed germ or a weakened germ that allows the body to form protection against that germ the next time the body is exposed that germ [176].
•Evidence of adverse effects related to exposure to multiple antigens is lacking. In a cohort of 1047 children who were exposed to an average of >10,000 antigens by age 24 months (predominantly through whole cell pertussis vaccine), there was no association between increasing antigen exposure and adverse neuropsychologic outcomes (eg, general intellectual function, speech and language, verbal memory, attention and executive function, tics, achievement, visual spatial ability, and behavior regulation) [175].
•The infant immune system can respond to multiple antigens (conservative estimates suggest thousands) simultaneously [61,173]. As examples:
-Mild to moderate illness does not interfere with an infant's ability to generate protective immune responses to vaccines.
-The immune response induced by combination vaccines is comparable to the response when the vaccines are administered separately.
•Avoiding vaccines does not improve a child's response to infections for which there are no vaccines (eg, enterovirus, Candida) [177-179]. In addition, in a small study, completely immunized and unimmunized children appeared to have equivalently robust innate and adaptive immune responses to nonantigen-specific stimuli (eg, pathogen-associated microbial patterns, generic T cell stimuli) [180].
•Children who develop infections for which there are no vaccines have vaccine antigen exposure that is similar to that of children who do not develop such infections (rather than greater exposure, as would be expected if exposure to vaccine antigens overwhelms the immune system). In a nested case-control study, estimated maximum single-day vaccine antigen exposure and cumulative vaccine antigen exposure before age two years were similar in children age 24 through 47 months who developed infections not prevented by vaccines and matched controls [62]. These findings support the safety of the routine immunization schedule, which often requires multiple vaccines at a single visit (figure 2A), and confirm that the schedule does not weaken the immune system.
●Vaccines are not necessary – As vaccine-preventable diseases become less common and parents have little familiarity with the devastating effects of vaccine-preventable diseases, some parents may believe that vaccines are not necessary [69]. These parents must be educated regarding the persistence of vaccine-preventable diseases, the potential for a rapid increase in vaccine-preventable disease incidence when immunization rates decline, and the potential complications of vaccine-preventable diseases [61]. (See 'Consequences of vaccine refusal' above and 'Risks of natural infection' above.)
Injection pain — Providers can allay parental concerns about pain by offering one or more of the available methods to reduce injection pain. (See "Standard immunizations for children and adolescents: Overview", section on 'Reducing injection pain'.)
Maintain relationship whenever possible — We encourage providers to make continuous and strident efforts towards educating parents who are vaccine hesitant, maintaining the relationship whenever possible. The decision to vaccinate ultimately belongs to the parents. The benefits of immunization must be weighed against those of the provider maintaining a positive relationship with the family. Maintenance of the relationship permits time for ongoing dialogue and targeted education and ensures that the child has a medical home. Ethical arguments for and against continuing care for children of vaccine-hesitant parents can be made [181,182]. (See 'Establish a positive dialogue' above and 'Target education' above.)
Although we encourage providers to maintain relationships with vaccine-hesitant families, we recognize that providers may have no option but to dismiss a family from their practice when poor communication and distrust are insurmountable [63,183]. This decision is not one that should be made lightly and should be made only after considering and respecting the parent's point of view. Factors influencing this decision include lack of shared goals, absence of trust in the clinician-family relationship, and concern that the child may subsequently contract a vaccine-preventable disease or transmit a vaccine-preventable disease to an individual who has vaccine contraindications or is too young to be immunized [181,184]. These concerns are particularly salient if community immunization rates are low and disease prevalence is high, or if the child has a medical predisposition to disease.
The 2016 AAP Clinical Report on countering vaccine hesitancy suggests that dismissal of a family should be an option of last resort, used only when [68,140,185]:
●The clinician has exhausted all means of education
●The family has been made aware of the policy regarding dismissal of nonvaccinators
●The geographic area is not in short supply of pediatric providers
●The practice provides sufficient information to help the family find another provider and continues to provide health care until the family does so (usually 30 days)
Alternative schedules — Alternative vaccine schedules are those that deviate from the recommended vaccine schedule (eg, in the United States, the schedule recommended by the CDC, AAP, and American Academy of Family Physicians (figure 2A-B)). Examples include the "selective vaccine schedule" and "alternative vaccine schedule" published by Dr. Robert Sears [186], as well as individual parental requests to postpone or skip one or more vaccines.
Unlike the CDC United States Recommended Immunization Schedule, alternative vaccine schedules offer incomplete and delayed protection against life-threatening diseases. For this reason, they should be considered only after other options have failed and the family would otherwise refuse vaccination entirely. Although alternative schedules may allay parental fears enough to permit immunization, they should not be used as a substitute for establishing parental dialogue or targeted education [68,69]. (See 'Establish a positive dialogue' above and 'Target education' above.)
Alternative schedules increase the duration of vulnerability to vaccine-preventable diseases that continue to cause outbreaks (eg, measles, pertussis), increase the risk of undervaccination, and may increase the risk of adverse effects [187-190]. They may require extra visits (ie, visits for immunization outside of the routine well-child visit schedule) that may be cumbersome and time-consuming.
A committee convened by the Institute of Medicine (now the National Academy of Medicine) to study the health outcomes related to the recommended childhood immunization schedule in the United States concluded that the schedule is safe and found no definitive evidence of adverse events related to multiple immunizations [191]. The schedules for individual vaccines have been demonstrated to be safe and effective.
Timely receipt of vaccines during the first year of life has no adverse effect on neuropsychologic outcomes. Review of data from the Vaccine Safety Datalink study, which included 1047 children, indicates that the 47 percent of children who received their vaccines on time (≥2 hepatitis B, three diphtheria-tetanus-pertussis, three H. influenzae type b, and two polio vaccines within 30 days of the recommended age) performed as well or better at age 7 to 10 years on every measure of neuropsychologic outcome than the 23 percent of children who received all of the recommended vaccines, but not on time, and the 20 percent of children who did not receive all of the recommended vaccines [192].
Precautions for unimmunized children — Children who have not been immunized are at risk to develop or transmit vaccine-preventable diseases. When they are ill, it is important for their parents to tell the health care provider that the child is unimmunized, particularly providers who are not familiar with their child's medical history or lack of immunizations (eg, on-call clinicians, emergency department clinicians). Determining the current immunization status is a necessary part of health care provider history-taking and assessment during every sick child encounter. This information allows the provider to consider vaccine-preventable diseases in the differential diagnosis and to prevent spread of vaccine-preventable diseases to other patients.
The CDC, AAP, and American Academy of Family Physicians have developed a handout to remind parents of the risks and responsibilities of refusing immunization [193]. Another handout is available from the Immunization Action Coalition (IAC).
Documentation — Providers should document each discussion with parents about the risks of not immunizing [140]. The AAP has developed guidelines for documentation and provides a sample "Refusal to Vaccinate" form (available through the AAP). Another sample form is available through the IAC [194].
PREVENTION — Strategies to prevent vaccine hesitancy have not been well studied. However, given that health care providers are an influential source of vaccine information, it is helpful for clinicians to establish open, honest, nonconfrontational dialogue about the importance of childhood vaccinations at the first interaction (ideally at the prenatal visit) [50,195,196]. We encourage providers to share their own or their practice's philosophy or policy for delaying or refusing vaccination to avoid the potential for future disagreements.
The dialogue should be continued at subsequent well-child visits. At each encounter, providers should listen to parental concerns to identify sources of misinformation or other factors that may lead to vaccine hesitancy. Providers can then provide individualized education to address specific concerns or misconceptions. (See 'Target education' above.)
Education should be multifaceted, with providers answering questions unambiguously, avoiding complicated statistics, and providing information that is easily understood and "personal." Some parents may find the information in the Vaccine Information Statements adequate to address their needs, but others may require more detailed scientific information or may find simple question-and-answer pamphlets or personal testimonials from vaccine advocates more helpful (table 1) [69,197]. (See 'Resources' below.)
Support for early vaccine education is provided by a randomized trial in which vaccine-hesitant parents (defined by a score of ≥25 on the Parent Attitudes about Childhood Vaccines [PACV] survey) who received educational information (a video, written information, and written instructions for finding accurate information on the internet) at the two-week health supervision visit had decreased PACV scores at the two-month visit compared with those who received usual care [198].
RESOURCES
●For vaccine-hesitant parents – Parents who need more information than the clinician can provide during an office visit can be directed to a number of reputable vaccine websites (table 1).
Focus groups suggest that most parents trust information from the Centers for Disease Control and Prevention (CDC) or American Academy of Pediatrics (AAP) [199].
Parent/family groups may be particularly helpful for vaccine-hesitant parents because they highlight identifiable, serious, and sometimes fatal consequences of refusing immunization, using anecdotes and visual imagery to counter those of children allegedly injured by vaccines [200].
●For health care providers – The CDC, in partnership with the AAP and the American Academy of Family Physicians, has developed Provider Resources for Vaccine Conversations with Parents. This website provides communication tips, vaccine safety information, answers to common questions. A related website provides specific information about vaccine-preventable diseases and the vaccines that prevent them that can supplement Vaccine Information Statements and guide parent risk-benefit discussions [69].
●The Vaccine Education Center at the Children's Hospital of Philadelphia provides a library of references that discuss vaccine safety and disprove claims made against vaccines.
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Immunizations in children and adolescents".)
SUMMARY AND RECOMMENDATIONS
●Vaccine hesitancy is a term used to describe refusal of vaccination or a delay in acceptance of vaccination. (See 'Definition' above.)
●Although the overall prevalence of complete vaccine refusal remains low (<2 percent), substantial numbers of parents refuse one or more vaccines or request that vaccines be administered on an alternative schedule. (See 'Epidemiology' above.)
●Concern about vaccine safety is the most common reason for vaccine refusal. Other parental concerns may focus on the belief that vaccines are not necessary or freedom of choice. (See 'General objections' above.)
●Vaccine refusal may result in vaccine-preventable disease in the individual and/or outbreaks of vaccine-preventable disease in unvaccinated and vaccinated individuals. (See 'Consequences of vaccine refusal' above.)
●Our approach to the management of vaccine hesitancy involves (see 'Approach to management' above):
•Establishing a positive dialogue – Approaching each patient encounter using positive nonconfrontational dialogue that presumes that the parents will ultimately vaccinate their child. (See 'Establish a positive dialogue' above.)
•Identifying parental concerns – Listening carefully and respectfully to identify parental concerns and the forces that influence parental concerns. (See 'Identify concerns' above.)
•Targeting education to address parental concerns – Targeted education may include education about vaccine effectiveness (figure 1), acknowledgment of vaccine limitations, providing accurate estimates of the risks of adverse events in the context of the risks of natural infection, correction of misconceptions, and discussion of techniques to alleviate injection pain. (See 'Target education' above and 'Resources' above.)
●We encourage providers to maintain relationships with families who refuse immunization but recognize that a provider may have no option but to dismiss a family from his or her practice when poor communication and distrust have become insurmountable. (See 'Maintain relationship whenever possible' above.)
●In the United States, we strongly support following the immunization schedule provided by the Centers for Disease Control and Prevention, American Academy of Pediatrics, and the American Academy of Family Physicians (figure 2A-B). Alternative schedules increase the duration of vulnerability to vaccine-preventable diseases. (See 'Alternative schedules' above.)
