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Vaccine rejection and hesitancy: a review and call to action
Tara C. Smith, PhD
The author declares she has no commercial or other association that might pose a conflict of
No financial support was provided for this manuscript.
Tara C. Smith, PhD
College of Public Health
Kent State University
Kent, OH 44242
Vaccine refusal has been a recurring story in the media for well over a decade. Though there is
scant evidence that refusal is genuinely increasing in the population, multiple studies have
demonstrated concerning patterns of decline of confidence in vaccines, the medical
professionals who administer vaccines, and the scientists who study and develop vaccines. As
specialists in microbiology, immunology, and infectious diseases, scientists are content experts
but often lack the direct contact with individuals considering vaccination for themselves or their
children that healthcare professionals have daily. This review examines the arguments and
players in the United States anti-vaccination scene, and discusses ways that experts in infectious
diseases can become more active in promoting vaccination to friends, family, and the public at
Keywords: vaccine hesitancy, vaccine denial, anti-vaccination, misinformation, internet
Background and Introduction
Since the late 1990s, concern has grown regarding a resurgence of the “anti-vaccine
movement,” a loosely-defined group of individuals who sow doubt about the effectiveness and
safety of vaccines. Though the most current iteration of this scare can be traced to the
publication of Andrew Wakefield’s (since-retracted) paper linking the measles-mumps-rubella
(MMR) vaccine to autism in 1998, anti-immunization sentiment in reality pre-dates the process
of vaccination, dating back to objections to the process of variolation in the early 18th century to
reduce smallpox morbidity and mortality [1, 2].
While vaccine rates have remained high in the United States as a whole [2, 3], national
surveys can overlook pockets of vaccine refusal which exist in many communities . Areas with
low vaccination rates have resulted in localized outbreaks of vaccine-preventable diseases,
including measles and pertussis . Measles cases in the U.S. reached a 20-year high in 2014
; 90% of those were among individuals who had not been vaccinated or whose vaccination
status was unknown [6, 7], suggesting the unvaccinated are drivers of outbreaks. Further,
vaccines are victims of their own success. Today, even many physicians have not seen a case of
measles, diphtheria, or other vaccine-preventable diseases; parents are a generation more
removed from the scourges that polio and rubella represented. As such, anti-vaccine activists
have been able to describe these diseases as harmless consequences of childhood, and vaccines
are presented as the danger rather than the disease.
Though public health and medical practitioners have been concerned about increasing
anti-vaccine sentiment, programs that have been implemented to change minds and attitudes
have been largely ineffective [8, 9].
This review aims to provide infectious disease experts with grounding in the current
rhetoric of vaccine denial; to introduce the cast of characters who play a role in perpetuating
vaccine misinformation and driving vaccine fear; and to discuss ways scientists can respond in
various venues to demonstrate support of vaccines and the very principles of vaccination.
The arguments against vaccination have changed little over time [1, 2]. These are
summarized in Table 1 and will be discussed here briefly. Most objections to vaccination are
currently cached in language that makes them highly palatable to parents and difficult for
scientists to object to, using terms such as “informed consent,” “health freedom,” and “vaccine
safety” . A recent article in Natural Mother Magazine makes it explicit that anti-vaccine
advocates should use language that frames vaccines as dangerous or unnatural, substituting
“vaccine-free” or “intact immune system” for “unvaccinated”, and “vaccine-associated diseases”
instead of “vaccine-preventable diseases” , for instance.
Many of the arguments focus on areas of distrust in medical science. They advance the
notion that vaccines are “unavoidably” dangerous because of nebulous “toxins” introduced into
the body via vaccination. Some of these chemicals are present in small amounts (aluminum as
an adjuvant, for example); others, such as “antifreeze,” are not and never have been present in
vaccines . Another commonly feared “toxin,” the ethyl mercury that is part of the
preservative thimerosal, has been removed from most routine vaccinations since 2001 (and was
never present in live vaccine formulations), despite no evidence of harm . Still, many argue
that children are purposely “poisoned” via vaccines because it benefits the bottom line of “Big
Pharma” and the physicians pharmaceutical companies work with.
Other arguments stem from misinformation regarding the immune system and vaccine
response, claiming vaccines “overwhelm” the immune system, and that natural immunity is
better than immunity induced by vaccines. The latter argument misses the point of vaccination
entirely, and the former ignores the fact that the body is seeded by thousands of species of
microbes and is exposed to countless antigens from birth onward; the relatively few additional
antigens introduced via vaccination are, relatively speaking, a drop in the bucket .
As a result of the spread and increased acceptance of these arguments, researchers have
documented reduced trust in medical practitioners by parents, and an increase in concerns
about vaccines. While only 19% of parents noted “concerns about vaccines” in a 2000 survey
, by 2009, 50% of parents had concerns  (reviewed in ).
The cast of characters
Though many parents may repeat uncritically the information they receive from vaccine
denial groups, these claims rarely originate with the parent de novo. As noted above, iterations
of the same arguments against and fears about vaccines have been employed for well over a
century, and are merely recycled and updated to better reflect the modern science landscape and
language. These updated vaccine myths are then circulated by a variety of influential individuals
and organizations (Table 2) and are read and repeated by parents and other media consumers.
Collectively, this “influencer” group has undue sway over the media when it comes to vaccine
information, as some media stories on vaccination strive for “balance” in reporting. As this idea
of “balance” is false —far more physicians and scientists support vaccines than not—the
same anti-vaccine individuals are interviewed for news pieces repeatedly, increasing their
exposure and profile in the news media.
Many of these “influencers” rely on the internet to spread their message (together, the
individuals and organizations included in Table 2 have over 7 million Facebook followers,
though some overlap in followers may be expected). Recent work has demonstrated that
approximately 80% of individuals use the internet yearly to search for health information ,
and relatively few discuss these findings with a healthcare professional. Kata  notes that
“common assertions found online included: that vaccines cause illness; that they are ineffective;
that they are part of a medical/pharmaceutical/government conspiracy; and that mainstream
medicine is incorrect or corrupt. Misinformation was widespread, in the form of inaccuracies or
outright deception.” While the effect of online misinformation on vaccination attitudes and
decision-making has not been carefully quantified, parents have often listed concerns similar to
those on anti-vaccine websites when asked by researchers why they did not vaccinate [20, 21],
suggesting permeation into community groups from anti-vaccine books and internet sites or
similar sources of misinformation. Further, even short exposure to vaccine-critical Internet sites
has been shown to increase perceived risks of vaccinating and minimize the risks of vaccine-
preventable diseases .
Though many of the individuals who spread vaccine misinformation are ordinary
citizens, the sources of most anti-vaccine tropes are individuals or groups who benefit from the
spread of such inaccuracies. Many of the primary anti-vaccine “thought leaders” have written
books or produced movies that characterize vaccines as dangerous and unsafe (see
Supplemental Information for examples of anti-vaccine books and sites). Others run groups
dependent on donations from individuals who support their ideas. Still others rely on clicks,
advertising revenue, and product sales from online sites where they share articles on the
“dangers” of vaccines. A recent analysis of anti-vaccination websites demonstrated that every
website examined except one “contained arguments against vaccination that could be
considered disingenuous” , supporting their role in the dissemination of misinformation
about vaccines. Further, “mommy blogs” in particular have been analyzed and found to tell
persuasive stories suggesting that vaccines pose a threat to children, which may be circulated to
large numbers of readers .
While many of the anti-vaccine arguments which parents refer to may ultimately stem
from or be promoted by such celebrities and/or websites, parents may not always believe or
know their information has been filtered through these individuals, nor that they have been
influenced by such. Additionally, an individual’s personal history of vaccination or medical care
for themselves or their children may also color their view of vaccinations, independent of or
reinforced by exposure to media on vaccines. There is wide heterogeneity in individuals who
doubt vaccines [17, 25], so while understanding individuals and groups involved in anti-vaccine
messaging is important, scientists should not assume that all individuals who express skepticism
about vaccines share the same background, media consumption, or views.
It should also not be assumed that individuals who question vaccines have merely
absorbed anti-vaccine messages (including those from the above sites and individuals) in a
vacuum. Both vaccine hesitancy and vaccine promotion are influenced by the social and cultural
contexts in which messages are received  as discussed below.
The spectrum of vaccine skepticism
There are many different sub-populations of individuals with divergent reasons for not
vaccinating or delaying vaccines . This may be due to a variety of factors, including
complacency (low risk perceptions of vaccine-preventable diseases); lack of convenient access to
vaccine services; or lack of confidence in vaccines due to concerns about safety and other vaccine
issues [25, 28].
While many may characterize all individuals who eschew vaccines as “anti-vaccine” or
“vaccine deniers,” in reality there is a broad spectrum of individuals who choose not to have
themselves or their children vaccinated. These range from individuals who are solidly anti-
vaccine, frequently termed “vaccine rejectors,” to those who may accept or even advocate for
most vaccines, but have concerns over one or more vaccines. Hagood and Mintzer Herlihy 
suggest a 3-category model, characterizing individuals as vaccine rejectors (VRj), vaccine-
resistant (VR), or vaccine-hesitant (VH). Vaccine rejectors are those who are “unyieldingly
entrenched in their refusal to consider vaccine information,” prone to conspiracy theory
thinking, and may eschew traditional medical providers altogether in favor of “complementary”
or “alternative” medical practices—and as such, very unlikely to change their opinions on
vaccines. The vaccine-resistant are those who may currently reject vaccination but are still
willing to consider information, and have a lower incidence of belief in conspiracy theories than
VRj individuals. Vaccine-hesitant individuals tend to have anxiety about vaccinations but are
not committed to vaccine refusal . These groups correspond roughly to the “refusers,”
“late/selective vaccinators,” and “the hesitant” identified in . Interventions targeted at
changing minds or attitudes in order to increase vaccine acceptance need to take into
consideration this spectrum of beliefs regarding vaccines in order to be properly tailored to the
targeted audience [26, 31], rather than assuming that all individuals with vaccine concerns have
a single cohesive belief system.
As the above demonstrates, there is no “one size fits all” model for responding to vaccine
hesitancy/denial. In the experience of the author, most of the ideas scientists commonly have
about vaccine rejection seem to fit in more with the “vaccine rejectors” group. While this group
may be the most vocal about their vaccine concerns, it is likely that they are in the minority in
the spectrum of individuals adverse to vaccines; Leask et al. suggest that less than 2% of all
parents are outright “refusers” . However, these active rejectors may cause damage in the
general public by amplifying myths and misinformation about vaccination and shift the opinions
of others away from vaccine acceptance .
What to do and how to respond as an expert lacking patient contact?
Most interventions in recent years have focused on the vaccine-hesitant. Vaccine
hesitancy has been defined as “delay in acceptance or refusal of vaccines despite availability of
vaccination services” , in order to separate them from individuals or children who may be
delayed on vaccines through lack of services or access rather than a philosophical belief. This
group is generally thought to be the most amenable to interventions, as they typically are not
solidly anti-vaccine and may be considered “fence-sitters” on many vaccine issues, who have not
strongly committed to either a “pro” or “anti” vaccine stance. Some concerns these parents
express over vaccines are seemingly minor, including pain during injections and fevers following
vaccination , but they may also have concerns about autism and the MMR vaccine, Guillain-
Barré syndrome and the influenza vaccine, or others .
Most articles examining interventions for the vaccine-hesitant were written with
healthcare providers as primary targets, e.g. [30, 34, 35]. While microbiologists and infectious
disease experts may not always have direct patient care responsibilities, they likely have
extensive knowledge of the concepts underlying vaccination, and of the diseases which vaccines
prevent. However, scientists do not always know the rhetorical tricks and tactics  that
vaccine rejectors and their leaders (see Table 2) frequently employ; engaging them can be a
mistake without understanding not only the science, but also the objections and references that
vaccine rejectors may use. Understanding the arguments and concerns that individuals have
about vaccines, and from where they originate, can allow for better communication regarding
vaccines on the part of scientists.
Furthermore, scientists should realize that engaging directly with active rejectors will be
very unlikely to change minds, though less is known about the effectiveness of this tactic on
“lurkers” or other readers or listeners who may be following along with a conversation but not
participating. Prior research has documented that exposure to social information online can
impact attitudes and behavior , though this has not been tested explicitly with readers of
vaccine information, either pro-vaccine or anti-vaccine.
As noted previously, one impulse many scientists may have is to simply educate the
public. Known as the “information deficit model” of science communication, this model assumes
that the public is merely uneducated or under-educated about vaccines, and that providing
additional factual information will fill this knowledge gap and lead people toward vaccinating
. Unfortunately, information alone has not been shown to increase vaccine confidence
among hesitant parents [9, 37].
This isn’t to suggest that providing knowledge is unimportant. Filling in data gaps and
acting as a reliable, factual source of information is an essential service to those genuinely
seeking science-based evidence about vaccination. This information can be communicated in
person with friends or family members (particularly those with shared values) [38, 39],
submitted to local newspapers as opinion pieces or letters to editors , or provided online
through blog posts, social media updates, or other sites on the internet, where it may be
inadvertently “stumbled upon” by searches or references from other links. Individuals should be
aware that such educational efforts are likely to backfire for individuals deeply entrenched in
vaccine rejection , but have been cited in “conversion” stories of individuals who moved
across the spectrum from vaccine doubter to advocate .
Further, the frequent use of conspiracy theory thinking among anti-vaccine thought
leaders engenders a lack of trust towards the medical and scientific communities. As such,
providing more education to some on the spectrum of vaccine refusal/hesitancy will be
ineffective , as it is unlikely to be sufficient to simply reassure many vaccine-hesitant
parents that expert groups have confirmed that vaccines are safe and effective when these
parents already distrust the “experts” .
Still, biomedical scientists who are vocal in their support for vaccines can serve to
cement the idea that vaccination is “normal” and expected. Kestenbaum and Feemster note that
a “…parent’s motivation to vaccinate their children is also influenced by social norms, which are
the rules that a group uses for appropriate and inappropriate values, beliefs, attitudes, and
behaviors” . A recent Pew survey found that 82% of U.S. adults agree that “healthy children
should be required to be vaccinated to attend school because of potential risk to others,” and
88% agree that vaccine benefits outweigh the risks . While vaccine hesitancy does exist,
vaccination on schedule is still the norm for the great majority of families. As a professional who
accepts vaccines as a part of life for yourself and your children, conveying that information to
your networks can help to subtly shift opinion on what Shelby and Ernst call “the greatest story
never told: the uneventful vaccination”  (see Figure 1). While stories of uncomplicated
vaccine administration are less likely to “go viral” than stories of injured children [43, 44], these
stories can further ingrain the idea that vaccines are being given every day without incident.
For those who want to get more deeply involved, Shelby and Ernst put forward the idea
of a “vaccine ambassador” program at physician offices . The authors noted that “There is a
growing passion among parents who vaccinate to begin speaking up about the importance of
immunization, and yet we continue to hear from these parents that they don’t know how to
help.” They suggest that physicians put a call out to their patients, and willing parents could
provide contact information that can be given to vaccine-hesitant parents. The “ambassadors”
would receive training and share the reasons why they decided to vaccinate their own children
. Particularly if this is done amongst individuals with shared values , such a program
may be beneficial.
Ambassadors may benefit from using the C.A.S.E. method outlined by Singer , which
includes steps to corroborate parents’ fears, offer information about the educator and their
personal experience with vaccines, provide information about the science regarding vaccines
and explain recommendations, all within a context of empathy and an established relationship
[29, 45]. A recent publication by Schoeppe et al.  involved parents as immunization
advocates to address vaccine hesitancy in Washington state, whose school entry exemption rate
was three times the national average. Though lacking a control group, they found that vaccine
hesitancy was reduced in their population, from 23% to 14%, and the number of parents who
agreed vaccination is a good idea rose. Scientists may adapt recommendations from papers
targeting healthcare professionals to work with such groups [30, 35].
Though many scientists may hesitate to “get political,” vaccine policy is set at the state
level; as such, privately contacting state legislators and advocating for the strengthening of
vaccine exemption policies is another way to protect herd immunity, as states with stricter
exemption criteria have higher rates of vaccination compliance . California recently passed
SB277, which eliminated religious and philosophical exemption for school admittance. In their
first year of data analysis, they found that vaccination rates rose in students attending
kindergarten 2.8 percentage points . Similarly in Michigan, state officials issued a regulation
requiring consultation with local health departments prior to obtaining a vaccine waiver,
resulting in 35% fewer vaccine exemptions in the first year . In each case, an outbreak may
have helped both to sway legislators and mobilize parents (the Disneyland measles outbreak in
California, and a large outbreak of pertussis associated with a Traverse City charter school in
Michigan), but one need not wait for an emergency situation in order to push state legislators to
strengthen vaccine regulations. This is one way scientists can work “behind the scenes,” to
advocate for and promote such legislation.
Academics can also examine vaccine policies at their own institutions. My current
institution requires only the MMR for admission, while many universities have more rigorous
vaccine requirements. The University of California system will expand their vaccine
requirements as of fall 2017, requiring students be vaccinated for hepatitis B, measles, mumps
and rubella; chicken pox; meningococcus; and tetanus, diphtheria and whooping cough prior to
registration. Advocating for vaccine protection for college students is another way scientists can
use their expertise to increase vaccination rates and demonstrate the importance of
Finally, while there may be no single leader of an anti-vaccine “movement,” many of
those listed in Table 2 are highly media-savvy and unafraid to push their opinions that vaccines
are dangerous, full stop. Scientists, by our training and often by our nature, are often loathe to
think of issues without bringing in shades of gray, while vaccine thought leaders frequently
express strict black-and-white thinking. Advocating for vaccines isn’t always easy; it may
necessitate leaving one’s comfort zone, and open one up as a target of harassment . But with
so much at stake, shouldn’t subject experts be on the forefront of this fight?
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Table 1. The arguments.
Vaccines are “toxic” and contain antifreeze, mercury, ether, aluminum, human aborted
fetal tissue, antibiotics, and other dangerous chemicals which can lead to autism and
an assortment of chronic health conditions. Slogan: “Green our Vaccines”.
Vaccines are a tool of “Big Pharma;” individuals who promote them are merely
profiting off of harm to children and/or paid off by pharmaceutical companies
A child’s immune system is too immature to handle vaccines; they are given “too many,
too soon” and the immune system becomes “overwhelmed,” leading to autism and an
assortment of chronic health conditions.
“Natural immunity is better;” most vaccine-preventable diseases are harmless to most
children, and natural exposure provides more long-lasting immunity. e.g., “I had the
chickenpox as a kid and I was just fine.” Some individuals may also have the mistaken
belief that all “natural” infections confer life-long immunity, while all vaccine-derived
immunity is short-lived.
Vaccines have never been tested in a true “vaccinated versus unvaccinated” study; the
vaccines in the current schedule have never been tested collectively.
Diseases declined on their own due to improved hygiene and sanitation; “vaccines
didn’t save us.”
Vaccines “shed” (can be transmitted by vaccinated individuals to others); therefore,
cases of vaccine-preventable diseases in the population are driven by the vaccinated,
not the unvaccinated.
Adapted from [2, 10, 23]; see Supplemental information for a list of comprehensive rebuttals.
Table 2: Thought Influencers in the Anti-Vaccine Movement
Former British physician; lead author of 1998 study in The Lancet
suggesting MMR vaccination led to autism , since retracted.
Discredited after an investigation into the study demonstrated
undisclosed conflicts of interest and unethical conduct;
subsequently, Wakefield lost his medical license. He currently lives
in United States and remains active promoting anti-vaccine ideas,
including the 2016 documentary VAXXED (see Supplemental
Information for books, movies, and web sites from anti-vaccine
thought influencers). Active on social media via the VAXXED page
(~67,000 followers on Facebook).
California physician, author of “The Vaccine Book”. Formulated an
“alternative” vaccine schedule which delays many vaccines from the
CDC recommended schedule; this schedule has been widely
promoted by other anti-vaccine activists and is often cited by
parents, and reinforces the idea that children receive “too many, too
soon” (see Table 1). Active on social media (~65,000 followers on
Private practice physician in Ohio, author of “Vaccines: The Risks,
the Benefits, the Choices, a Resource Guide for Parents” and
“Saying No to Vaccines: A Resource Guide for All Ages”. Co-
founder of the International Medical Council on Vaccination
(http://www.vaccinationcouncil.org/), whose purpose is to “counter
the messages asserted by pharmaceutical companies, the
government and medical agencies that vaccines are safe, effective
and harmless.” Active on social media (~215,000 followers on
Private practice physician at “The Center for Disease Prevention
and Reversal” in Illinois; prior vice-president of the American
Institute of Homeopathy. Featured in Oprah.com and the recent
web series “The Truth about Vaccines.” Active on social media
(~6,000 followers on Facebook).
Private practice physician in Maine and Virginia, author of
“Dissolving Illusions: Disease, Vaccines and the Forgotten History”.
Active on social media (~31,000 followers on Facebook).
Private practice and holistic/integrative physician in New York.
Featured in the web series “The Truth about Vaccines” and the anti-
HPV vaccine documentary “The Greater Good”. Active on social
media (~13,000 followers on Facebook).
Former private practice physician in Illinois, runs the website and
business Mercola.com. Author of “The Great Bird Flu Hoax: The
Truth They Don't Want You to Know About the ‘Next Big
Pandemic’". Founder of “Health Liberty” (“A nonprofit coalition
formed by Mercola.com, National Vaccine Information Center,
Fluoride Action Network , Institute for Responsible Technology ,
Organic Consumers Association, and Consumers for Dental Choice,
to help protect every American's freedom to make voluntary health
choices”. Active on social media (~1,600,000 followers on
Actress and comedian, “Mommy warrior,” Generation Rescue
spokesperson, parent of autistic child. Author of “Louder Than
Words: A Mother's Journey in Healing Autism”; “Mother Warriors:
A Nation of Parents Healing Autism Against All Odds”; and
“Healing and Preventing Autism: A Complete Guide”. Active on
social media (~1,100,000 followers on Facebook).
Activist and parent of autistic child, co-founder of Generation
Rescue and co-founder and contributor to the Age of Autism blog.
Both organizations suggest that vaccines are a major factor driving
the development of autism. Active on social media (~25,000
followers on Facebook).
Environmental lawyer, author of “Thimerosal: Let the Science
Speak” and controversial 2005 article, “Deadly Immunity,”
published in Rolling Stone and Salon but later retracted. Reported
in 2017 to have been appointed to lead a vaccine safety commission
for President Trump. Active on social media (~20,000 followers on
Activist and founder of the National Vaccine Information Center
(NVIC), originally Dissatisfied Parents Together (DPT). Fisher
began speaking out against vaccines after her son suffered what she
believes is a vaccine injury. Co-author of “A Shot in the Dark” and
“Vaccines, Autism & Chronic Inflammation: The New Epidemic”.
Via the NVIC, Fisher is active in tracking and responding to local
and state vaccine-related legislation. Active on social media via the
NVIC (~193,000 followers on Facebook).
Nutrition and parenting blogger who has dubbed herself the
“Healthy Home Economist.” Appeared on the “Late Show with Jon
Stewart” to defend her anti-vaccine stance. Active on social media
(~155,000 followers on Facebook).
Mother of five, naturopath, and “wellness” blogger at “Living
Whole.” Heimer posts self-declared “common sense” information
about healthy living, which includes avoiding vaccines. Active on
social media (~26,000 followers on Facebook).
Mother of five, cooking and parenting blogger at “Modern
Alternative Mama;” sells “health and wellness” products at
Earthley.com. Active on social media (~70,000 followers on
The “Food Babe;” influential “food safety” advocate who and social
media star who has argued against vaccines. Hari recently had her
first child and joined the ranks of the “mommy bloggers,”
recommending against vaccines. Instead of accepting the influenza
vaccine during pregnancy, she recommended “wash hands often,
reduce stress, exercise, drink lots of filtered water, eat fermented
foods, and avoid industrial toxins”. Active on social media
(~1,200,000 followers on Facebook).
Owner/operator of “Natural News” website; has dubbed himself
“The Health Ranger.” Adams is a key purveyor of conspiracy
theories, suggesting the government is lying to the public about
vaccines, Ebola, influenza, and much more, simultaneously denying
Zika exists and profiting from Zika mosquito repellent
Figure 1: Examples of photos posted to the author’s social media accounts. Panel A: The author
(middle) and her older children after receipt of seasonal influenza vaccines. Panel B: The
author’s youngest child at Walt Disney World, wearing a shirt saying “Fully Vaccinated. You’re
Welcome.” Both techniques can serve as conversation-starters around vaccination.