A broken trust: lessons from the vaccine--autism wars.
ABSTRACT Researchers long ago rejected the theory that vaccines cause autism, yet many parents don't believe them. Can scientists bridge the gap between evidence and doubt?
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ABSTRACT: Data are limited on whether providers understand parental attitudes to recommended childhood immunizations. We determined parental attitudes and assessed how accurately providers estimated parental opinions. Survey of parents and providers (pediatricians, nurses, medical assistants) in randomly selected practices in Houston, Texas. Surveys assessed demographics, perceptions of immunization importance, safety and efficacy, and acceptability of vaccine delivery. Providers estimated parental responses. 401 parents (82% mothers, 12% fathers, 6% other) and 105 providers participated. Parents thought vaccines were important for health (median score 9.5; 0=not important, 10=extremely important) but also were concerned regarding vaccine safety and side effects (8.9 on 0-10 scale). 309 (77%) agreed that vaccines effectively prevent disease. Route of administration mattered to 147 (37%), who preferred injection (9.0) over oral (7.3) or intranasal (4.8) routes. Although parents would prefer three or fewer injections per visit, preventing more diseases (189 [47.6%]) was more important than number of injections (167 [42.3%]) when deciding the number of vaccines allowed per visit. White parents rated vaccines less important in preventing some illnesses than did non-white (P≤0.006 for meningitis, hepatitis, HPV, influenza and rotavirus) and rated number of injections per visit more important than number of diseases prevented (51.6% white versus 34.2% non-white; P 0.002). Providers underestimated parental attitudes toward vaccine importance (particularly influenza and HPV), and overestimated the proportion of parents who thought route of administration mattered (63%) and that number of injections per visit was the most important factor (76%) around parental vaccine decisions (P<0.001 for parent-provider mismatch). Most surveyed parents believe vaccines are important for child health and rate disease prevention higher than number of injections entailed. Providers underestimate the importance of some vaccines to parents and overestimate parental concerns regarding route of administration. Future research should focus on how this mismatch impacts parental vaccine decisions.Vaccine 12/2013; · 3.49 Impact Factor
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ABSTRACT: This article demonstrates how misinformation concerning autism and vaccinations was created and suggests that social workers may be perfectly poised to challenge pseudoscience interpretations. Utilizing social network theory, this article illustrates how erroneous research, mass media, and public opinion led to a decreased use of vaccinations in the United States and a seven-fold increase in measles outbreaks. It traces the dissemination of spurious research results and demonstrates how information was transmitted via a system of social network nodes and community ties. This article encourages social workers, as frontline knowledge brokers, to counter misinformation, which may lead to significant public health consequences.Journal of Evidence-Based Social Work 05/2014; 11(3):269-74.
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ABSTRACT: There has been a substantial increase in research activity on autism during the past decade. Research into effective ways of responding to the immediate needs of autistic people is, however, less advanced, as are efforts at translating basic science research into service provision. Involving community members in research is one potential way of reducing this gap. This study therefore investigated the views of community involvement in autism research both from the perspectives of autism researchers and of community members, including autistic adults, family members and practitioners. Results from a large-scale questionnaire study (n = 1,516) showed that researchers perceive themselves to be engaged with the autism community but that community members, most notably autistic people and their families, did not share this view. Focus groups/interviews with 72 participants further identified the potential benefits and remaining challenges to involvement in research, especially regarding the distinct perspectives of different stakeholders. Researchers were skeptical about the possibilities of dramatically increasing community engagement, while community members themselves spoke about the challenges to fully understanding and influencing the research process. We suggest that the lack of a shared approach to community engagement in UK autism research represents a key roadblock to translational endeavors.PLoS ONE 01/2014; 9(10):e109946. · 3.53 Impact Factor
A Broken Trust: Lessons from the Vaccine–Autism Wars
Researchers long ago rejected the theory that vaccines cause autism, yet
many parents don’t believe them. Can scientists bridge the gap between
evidence and doubt?
Senior Science Writer/Editor, PLoS Biology, Public Library of Science, San Francisco, California, United States of America
Until the summer of 2005, Sharon Kaufman had never paid
much attention to the shifting theories blaming vaccines for a
surge in reported cases of autism. Kaufman, a medical
anthropologist at the University of California, San Francisco,
knew that the leading health institutions in the United States had
reviewed the body of evidence, and that they found no reason to
think vaccines had anything to do with autism. But when she read
that scientists and public officials who commented on the studies
routinely endured malevolent emails, abusive phone calls, and
even death threats, she took notice.
‘‘Hecklers were issuing death threats to spokespeople,’’ Kaufman
exclaims, ‘‘people who simply related the scientists’ findings.’’ To a
researcher with a keen eye for detecting major cultural shifts, these
unsettling events signaled a deeper trend. ‘‘What happens when
the facts of bioscience are relayed to the public and there is
disbelief, lack of trust?’’ Kaufman wondered. ‘‘Where does that
Struck byhow the idea ofa vaccine–autismlink continuedtogain
cultural currency even as science dismissed it, Kaufman took a 26-
month hiatus from her life’s work on aging and longevity to
investigate the forces fueling this growing divide between scientists
and citizens (see Figure 1). She wanted to understand how parents
thought about risk and experts, how these attitudes shaped parents’
decisions about vaccination, and what the vaccine wars might teach
us about the long-term erosion of public trust in science.
Key events in the US and Britain led parents in both countries
to favor different, unproven vaccine–autism theories. In the UK,
confidence in the measles, mumps, rubella (MMR) vaccine
plummeted after British gastroenterologist Andrew Wakefield held
a press conference to promote his hypothesis that the measles virus
caused a leaky gut, sending toxic substances into the bloodstream
and, ultimately, the brain. Separating the MMR into three
individual vaccines would be safer, he said. Wakefield’s idea
expanded on a finding of intestinal disease in children with autism
that was published in a now discredited 1998 Lancet paper . At
press time of this Feature, Wakefield faces charges of serious
professional misconduct before the General Medical Council
(GMC) for allegedly violating ethical research practices on several
counts. The GMC is also investigating allegations that Wakefield
failed to disclose conflicts of interest—including a pending patent
on a rival measles vaccine . (He has denied any wrongdoing.)
In the US, fears centered around the ethylmercury-containing
preservative thimerosal after a 1999 government report revealed
that three childhood vaccines—diphtheria, tetanus, acellular
pertussis (DTaP); Haemophilus influenzae type b (Hib); and hepatitis
B—might expose infants to more mercury than anyone had
realized. (Thimerosal, 49.6% ethylmercury by weight, was never
in vaccines with live attenuated virus, including MMR.) Based on
this finding, a speculative article published in a fringe medical
Published May 26, 2009
* E-mail: firstname.lastname@example.org
Figure 1. Sharon Kaufman. For most of her academic career,
Kaufman, a professor of medical anthropology at the University of
California, San Francisco, has studied major cultural trends related to
health and aging. She saw the vaccine–autism controversy as an
opportunity to understand how cultural factors shape issues of trust,
risk, and responsibility as they relate to science. (Photo credit: Eliot
Copyright: ? 2009 Liza Gross. This is an open-access article distributed under
the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the
original author and source are credited.
Citation: Gross L (2009) A Broken Trust: Lessons from the Vaccine–Autism
Wars. PLoS Biol 7(5): e1000114. doi:10.1371/journal.pbio.1000114
PLoS Biology | www.plosbiology.org1 May 2009 | Volume 7 | Issue 5 | e1000114
journal spawned the theory that autism might be a form of
vaccine-induced mercury poisoning.
Now, more than ten years after unfounded doubts about
vaccine safety first emerged, scientists and public health officials
are still struggling to set the record straight. But as climate
scientists know all too well, simply relating the facts of science isn’t
enough. No matter that the overwhelming weight of evidence
shows that climate change is real, or that vaccines don’t cause
autism. When scientists find themselves just one more voice in a
sea of ‘‘opinions’’ about a complex scientific issue, misinformation
takes on a life of its own.
Knowing that fears about MMR could easily spread in
America, US public health officials had acted quickly to address
festering doubts about vaccines. Officials at the Centers for
Disease Control and Prevention (CDC), hoping to allay ongoing
concerns that the agency couldn’t objectively monitor vaccine
safety while also advocating immunization, had asked the nation’s
leading independent advisor on science and health policy, the
Institute of Medicine (IOM), for help. The IOM convened a safety
review panel in 2000—explicitly excluding experts with a vested
interest in vaccine safety—to address ‘‘topics of immediate and
intense concern’’ .
In its first review, the IOM panel found no evidence of a causal
relationship between MMR and autism ‘‘at the population level,’’
but couldn’t rule out the possibility that it might contribute to
autism spectrum disorders (ASDs) in a subset of children. Moving
on to thimerosal, the panel determined that the available evidence
was ‘‘inadequate to accept or reject a causal relationship between
thimerosal and the disorders of autism, attention deficit, and
speech and language delay’’ .
Meanwhile, CDC scientists continued their investigations of
vaccine safety—prompting an angry backlash. After releasing a
2003 study of more than 140,000 children that showed no
relationship between thimerosal and autism, the CDC received
such disturbing threats that agency officials called in federal
investigators . (The CDC split its advocacy and safety
monitoring branches in 2005 in an effort to restore public trust.)
By 2004, the IOM panel had reviewed over 200 epidemiological
and biological studies for any link between vaccines and autism. In
its eighth and final report, the panel unanimously determined that
there was no evidence of a causal relationship between either
MMR or thimerosal and autism, no evidence of vaccine-induced
autism in ‘‘some small subset’’ of children, and no demonstration
of potential biological mechanisms. Considering the matter
resolved, the panel recommended that ‘‘available funding for
autism research be channeled to the most promising areas’’ .
The report should have delivered the final blow to the vaccine–
autism theories. Instead, it gave anti-vaccine activists a new target.
An online group called Parents Requesting Open Vaccine
Education—or PROVE, a not-so-subtle challenge to scientists to
‘‘prove’’ that vaccines don’t cause autism—posted a roundup of
parents’ groups denouncing the IOM panel as ‘‘riddled with
conflicts of interest’’ and urged parents to spread the word that
panelists conspired ‘‘to sweep a generation of children under the
rug and maintain current vaccine policy at any and all cost’’ .
Despite overwhelming evidence that vaccines don’t cause
autism, one in four Americans still think they do . Not
surprisingly, the first half of 2008 saw the largest US outbreak of
measles—one of the first infectious diseases to reappear after
vaccination rates drop—since 2000, when the native disease was
declared eliminated (see Figure 2). Mumps and whooping cough
(pertussis) have also made a comeback. Last year in Minnesota,
five children contracted Hib, the most common cause of
meningitis in young children before the vaccine was developed
in 1993. Three of the children, including a 7-month-old who died,
hadn’t received Hib vaccines because their parents either refused
or delayed vaccination.
The same trends have played out in Britain, where one in four
parents told pollsters in 2002 that they believed ‘‘the weight of
scientific evidence supports a link between MMR and autism’’ .
Though state law in the US requires that children be vaccinated to
enter school or daycare (although parents may cite philosophical
and religious reasons to claim exemptions), vaccination is not
compulsory in Britain, and vaccination rates for MMR there
dropped from 92% in 1998 to 80% by 2003. Although rates
climbed back to 85% in 2006, England and Wales last year saw
1,000 measles cases before winter, breaking a ten-year record .
(Immunization rates for other childhood vaccines in Britain were
largely unaffected by the MMR scare.)
Outbreaks in both countries involved primarily children who had
received only one of the two recommended MMR shots or had not
been vaccinated at all. US health officials traced the vast majority of
2008’smeasles casesto unvaccinated Americans whocontracted the
infection in Europe—and noted that thespike wasduenot to a large
number of imported cases, but to increased viral transmission
among unvaccinated children after importation into the US.
Seeds of Doubt
Kaufman sees the enduring belief in the vaccine–autism theory
as an example of what Ludwik Fleck, a clinical microbiologist with
a passion for epistemology, called ‘‘an event in the history of
thought’’—a critical step in the way the perception of a scientific
fact changes . In the US, that first step came in the form of a
simple legislative action that produced new information about
what was in vaccines—and quickly fed speculative theories linking
them to autism.
In 1997, a US congressman from New Jersey inserted into a
funding bill a provision that gave the Food and Drug
Administration (FDA) two years to measure levels of mercury in
all products under its jurisdiction, and release its findings to
Congress and the public. The FDA’s analysis revealed that
because several new vaccines were added to the immunization
schedule after 1988, some infants could be exposed to as much as
187.5 micrograms of ethylmercury by the time they were
6 months old—if every dose of Hib, hepatitis B, and DTaP
contained thimerosal .
Based on this new finding, says Kaufman, leading vaccine experts
began to investigate the possibility that mercury in vaccines was
putting kids at risk. While the ethylmercury levels exceeded the
federal safety guidelines for methylmercury, which gains toxicity as
it accumulates through the food chain, no guidelines existed for
ethylmercuryatthetime.Its toxicitywas largelyunknown;however,
there was evidence that very high doses of ethylmercury could cause
neurological damage. It was also known that methylmercury can
cause subtle neurological effects in infants born to mothers who eat
large amounts of fish andwhale meat.Studies havesince shown that
ethylmercury is eliminated much faster than methylmercury and is
unlikely to accumulate. But in 1999, no one knew what dose to
consider safe for the developing brain.
Given the uncertainty about ethylmercury’s toxicity, Neal
Halsey, director of the Institute for Vaccine Safety at Johns
Hopkins University, urged vaccine policymakers at the CDC and
American Academy of Pediatrics (AAP) to remove thimerosal from
vaccines as a precautionary measure and to maintain public
PLoS Biology | www.plosbiology.org2May 2009 | Volume 7 | Issue 5 | e1000114
confidence in their safety. The agencies agreed, and vaccine
manufacturers responded quickly; by March 2001, no children’s
vaccines contained thimerosal.
Anticipating the FDA’s release of its findings, the AAP issued a
statement explaining its decision as an effort to minimize children’s
exposure to mercury, asserting that ‘‘current levels of thimerosal
will not hurt children, but reducing those levels will make safe
vaccines even safer’’ . Unfortunately, Kaufman says, ‘‘rather
than reassuring parents, the statement fueled public fears and
prompted all sorts of questions.’’
To Halsey, one of the most respected figures in the vaccine
world, simply ignoring the FDA’s findings was not an option. He
hoped the rapid response would demonstrate the government’s
‘‘commitment to provide the safest vaccines possible’’ . But it
was too late for reassurances. Several months later, Medical
Hypotheses—an unconventional journal that welcomes ‘‘even
probably untrue papers’’—received and later published a purely
speculative article called ‘‘Autism: a novel form of mercury
poisoning’’ . Two of the authors, Sallie Bernard, a marketing
consultant, and Lyn Redwood, a nurse, had just launched the
parents’ advocacy group SafeMinds to promote their thimerosal
hypothesis. Although their now debunked theory appeared in a
journal that openly eschews peer review and evidence-based
observations, several parent advocacy groups still cite it as
evidence that mercury in vaccines causes autism.
No one disputes that methylmercury can cause subtle
neurological effects under specific conditions. But ‘‘these effects
were grossly exaggerated,’’ Halsey says. ‘‘It was a very large leap of
logic to the hypothesis that thimerosal caused autism.’’
Had the discovery about thimerosal come at a different time, it
might have gone unnoticed, suggests Jeffrey Baker, a pediatrician
and the director of the Program in the History of Medicine at Duke
Figure 2. Publicizing a life-saving technology. Before 1963, when the measles vaccine became available, each year approximately 3 to 4 million
cases, and an average of 450 deaths, were reported in the US. Thanks to the success of vaccination campaigns—publicized with a wealth of quirky
promotional materials (above)—measles is no longer endemic in the US, though it is widespread in other countries. Last year, the US saw the largest
outbreak of measles since the disease was declared eliminated in 2000; public health officials traced the majority of cases to unvaccinated Americans
who imported the disease from Europe. Despite the availability of a safe, cost-effective vaccine, measles remains a leading cause of death among
young children worldwide. Vaccination efforts resulted in a 74% global reduction in measles deaths between 2000 and 2007, according to the World
Health Organization, yet 197,000 children died in 2007—that’s nearly 540 a day.
PLoS Biology | www.plosbiology.org3 May 2009 | Volume 7 | Issue 5 | e1000114
University. He argues that rising autism rates, an expanded vaccine
schedule, and contemporary attitudes toward environmental risk
combined to create what he terms ‘‘a perfect storm’’ .
Since the 1980s, autism diagnoses in the US rose from about
0.47 per 1,000 children to about 6.7 per 1,000 today—about 1 in
150 kids. There’s a perception that environmental factors explain
this rapid increase, says Baker, but you don’t have to go back very
far to see how much the definition has expanded since Leo Kanner
first described autism in 1943 (see Box 1). Asperger disorder wasn’t
even part of the classification scheme until 1994. ‘‘Some people say
that Asperger’s accounts for 50% of cases,’’ says Simon Baron-
Cohen, director of the Autism Research Centre at Cambridge
University. ‘‘If that’s true, that’s added at least half of the
Parents who think environmental factors are behind rising rates
of autism see vaccines as the most obvious environmental exposure
to have changed, Baker says. In 1983, infants were vaccinated
against seven diseases; today, they receive 14 vaccinations, for a
total of 26 shots by age two. ‘‘This is the single most important
factor that drives parents to suspect vaccines,’’ Baker says.
In January, Baker appeared on an Oregon radio call-in show
that featured several parents who shunned vaccination. While over
95% of Oregon parents vaccinate their children, only 70% did so
last year in Ashland, a small town known for its Shakespeare
festival. Nearly 60% of Ashland residents polled told the CDC, in
town to hear parents’ concerns, they ‘‘would expect serious
consequences’’ from vaccines. Such low vaccination rates worry
public health officials because they could signal the next epicenter
of an epidemic: when vaccination rates drop below a critical
percentage, called the ‘‘herd immunity threshold,’’ infection can
swiftly spread among unprotected individuals. This threshold
varies depending on the vaccine and target disease; for example,
the target for measles, one of the most contagious human diseases,
is 90% .
After hearing several parents explain why they don’t vaccinate,
Baker pointed out that parents who claim nonmedical exemptions
seem to become so focused on their own children that they ‘‘lose
the bigger picture,’’ not accepting responsibility for the impacts
their actions may have on the health of the community. Reflecting
on the radio show, Baker says, ‘‘it really hit me hard. Many of
these parents who aren’t vaccinating their children are just
convinced that there’s something in the vaccines that is poisoning
The same month Kaufman learned that vaccine experts were
getting death threats, an inflammatory piece alleging a dark
conspiracy to cover up a vaccine–autism ‘‘scandal’’ ran simulta-
neously in Rolling Stone and the online magazine Salon—both of
which subsequently corrected ‘‘several inaccuracies.’’ Written by
Robert F. Kennedy, Jr., son of the slain US senator and
presidential candidate, ‘‘Deadly Immunity’’ accused government
officials of concealing evidence that mercury in vaccines ‘‘may
have caused autism in thousands of kids’’ to protect drug
companies from lawsuits.
The article came on the heels of a book called Evidence of Harm,
by David Kirby, that dramatized the story of a small group of
parents who ‘‘never abandoned their ambition to prove that
mercury in vaccines is what pushed their children, most of them
boys, into a hellish, lost world of autism.’’ Among the parents
profiled were Medical Hypotheses authors Bernard and Redwood.
That summer, Kennedy and Kirby hit the media circuit,
leveraging RFK Jr.’s celebrity to explain why parents should fear
vaccines. Remarkably, the major US public health institutions—
including the Surgeon General, Department of Health and
Human Services (DHHS), and National Institutes of Health—
made no effort to reassure the public that vaccines are safe and
could not cause the complex neurodevelopmental problems
associated with autism. As Kennedy and Kirby trumpeted their
largely uncontested claims, more parents filed lawsuits in federal
court claiming that vaccines injured their children.
By June 2007, the parents of nearly 5,000 children with autism
had sued for compensation under the Vaccine Injury Compen-
sation Program (VICP). The program was created in 1986, after
numerous lawsuits prompted by a pertussis vaccine scare forced
manufacturers to flee what they considered a low-profit, high-
liability market. It aimed to safeguard the nation’s vaccine supply
by limiting companies’ liability while compensating those who
experienced an adverse reaction. Although vaccines can cause
several known side effects (listed in a vaccine injury table),
including anaphylactic shock and even death, such events are
extremely rare. For example, the risk of a serious allergic reaction,
the most severe side effect for MMR, is less than 1 in a million.
The risks of not vaccinating are far greater: before the measles
vaccine became available in the US in the mid-1960s, 450 people
died and 4,000 suffered acute inflammation of the brain each year.
DHHS doctors decide whether a ‘‘table injury’’ was likely caused
by a vaccine. Claims regarding conditions that are not listed in the
table, like autism, are heard by lawyers.
The DHHS conceded in November 2007 that vaccines
aggravated an underlying mitochondrial disorder in the baby girl
of a Georgia couple, Terry and Jon Poling, ultimately causing
‘‘regressive encephalopathy with features of autism spectrum
disorder.’’ Their decision was in line with previous table injury
rulings that a measles-containing vaccine can exacerbate an existing
encephalopathy—in this case, caused by a mitochondrial enzyme
deficit. The condition shares symptoms with ASD, but is distinct.
Figure 3. From heroes to villains. When researchers announced in
1955 that a nationwide trial showed that the first polio vaccine was safe
and effective, inventor Jonas Salk was greeted as a national hero. Today,
rotavirus vaccine inventor Paul Offit (right, with co-inventor H. Fred
Clark) routinely endures vitriolic attacks on his credibility, along with
death threats, for defending the safety of vaccines. (Photo credit: The
Children’s Hospital of Philadelphia).
PLoS Biology | www.plosbiology.org4May 2009 | Volume 7 | Issue 5 | e1000114
The previous year, a case study published in the Journal of
Childhood Neurology  described developmental regression and
mitochondrial dysfunction in a child with autism. Jon Poling, a
neurologist, was the lead author. He failed to disclose that the
patient was his daughter or that he had a claim pending before the
vaccine court . Although the DHHS did not concede that
vaccines contributed to autism, the Polings told CNN in March
2008 that the ‘‘case may well signify a landmark decision with
children developing autism following vaccinations.’’
Activists welcomed the case as proof that vaccines cause autism
and several mainstream news outlets reported their opinions as a
legitimate side of the ongoing ‘‘controversy.’’ In April of 2008,
CNN’s Larry King hosted a show on the vaccine–autism ‘‘debate’’
featuring Jenny McCarthy, a celebrity ‘‘autism mom’’ promoting a
book about her son Evan’s ‘‘recovery’’ from autism. McCarthy
told King that she speaks to thousands of moms every weekend
who relay the same experience: ‘‘I came home, he had a fever, he
stopped speaking, and then he became autistic.’’ ‘‘It’s time to start
listening to parents who watched their children descend into
autism after vaccination,’’ she urged, because ‘‘parents’ anecdotal
information is science-based information.’’ McCarthy said the
Poling decision proved that ‘‘vaccines can trigger autism.’’ No
scientists were on hand to challenge her.
‘‘There’s a lot of good autism research out there,’’ says Paul
Offit, chief of infectious diseases at Children’s Hospital of
Philadelphia and head of the hospital’s Vaccine Education Center
(see Figure 3). ‘‘But you never hear about it because the anti-
vaccine movement has taken this issue hostage.’’ Offit has turned
down requests to appear on any show with McCarthy. ‘‘Every
story has a hero, victim, and villain,’’ he explains. ‘‘McCarthy is
the hero, her child is the victim—and that leaves one role for you.’’
Offit’s outspoken defense of vaccines, and especially his recent
book, Autism’s False Prophets, has made him public enemy number
one to many who think vaccines harmed their children. Even
before writing the book, Offit’s advocacy work earned him hate
mail and death threats. His critics especially malign him for co-
inventing and patenting the rotavirus vaccine, developed after a
25-year quest to prevent a disease that annually kills 600,000
Box 1. Autism at a Glance
Autism spectrum disorders (ASDs) are a collection of
conditions characterized by stereotyped behaviors and
narrow interests and pervasive problems with communica-
tion and social interactions. Symptoms typically emerge
before age three and range from a severe form, called
autistic disorder, to a much milder form, Asperger disorder.
Though researchers can’t point to any one cause of autism,
mounting evidence implicates genetic factors. ‘‘We’re seeing
a new gene association published almost every month,’’ says
Simon Baron-Cohen (see Figure 4). ‘‘We know it’s not a
single-gene disorder, but we don’t know if it’s ten genes or a
hundred genes.’’ Researchers also don’t know how these
genes function or interact with environmental factors.
Preliminary evidence suggests that autism may result from
disruptions in brain development caused by defects in
genes involved in regulating brain growth and neuron
In a 100-word definition published in the British Journal of
Psychiatry last year , Baron-Cohen noted that children
with Asperger disorder have average or above average IQ
and ‘‘average or even precocious age of language onset.’’ In
ASD, he wrote, many areas within the ‘‘social brain’’ are
atypical, so that children may have ‘‘a profile of impaired
empathy alongside strong ‘systemising’. Hence, [ASD]
involves disability (when empathy is required) and talent
(when strong systemising would be advantageous).’’ Baron-
Cohen recommended developing interventions that harness
systemizing to enhance empathy to help keep children on
track. A number of behavioral and educational interventions
may also minimize symptoms.
Because autism is far more common in males, Baron-Cohen
has been exploring factors that affect sex differences in
behavior to explain male vulnerability. Looking at individual
variations in sociability in typically developing children, his
group examined fetal testosterone (FT) levels from amniotic
samples and found that the higher the children’s FT levels,
the less eye contact they made, the slower they developed
language, and the more difficulty they had with empathy
. None of these differences presented at clinical levels.
Now that these kids are old enough to tolerate getting into
a brain scanner, Baron-Cohen can start looking at brain
structure and function to see how the results relate to FT
‘‘One strategy will be to identify which brain regions differ
between males and females,’’ he explains, ‘‘and which ones
seem to be associated with testosterone. That will provide a
set of regions to study in autism to see if you find the same
pattern of sex differences in autism.’’
Thanks to a collaboration with a group in Denmark, Baron-
Cohen now has access to enough amniotic fluid samples to
ask whether children diagnosed with autism have elevated
FT levels. He hopes to have the results next year, but is
careful to point out that FT will likely be just one piece of a
very complicated jigsaw. ‘‘We’re still in early days,’’ he says.
Figure 4. Simon Baron-Cohen. (Photo credit: Brian Harris).
PLoS Biology | www.plosbiology.org5May 2009 | Volume 7 | Issue 5 | e1000114
children worldwide. ‘‘If you want to make a vaccine, you have to
go to a pharmaceutical company,’’ he says. ‘‘But that instantly
makes you evil.’’
A Bridge Too Far?
Kaufman sees the persistence of the vaccine–autism theory as a
consequence of how individuals manage risk in modern society.
People must trust experts to protect them from risk, whether
they’re getting on an airplane or vaccinating their kids, she
explains. When faith in experts erodes, personal responsibility
prevails. ‘‘People think if you blindly follow experts, you’re not
taking personal responsibility,’’ she adds.
Offit blames the media for keeping the myth alive by following
the ‘‘journalistic mantra of ‘balance,’ ’’ perpetually presenting two
sides of an issue even when only one side is supported by the
science. And shows like ‘‘Larry King Live’’ have been ‘‘just awful
on this issue,’’ he adds, placing ratings and controversy above
public health by repeatedly giving McCarthy and other ‘‘true
believers’’ a platform to peddle fear and misinformation. But Offit
also wishes scientists would do a better job of communicating
theoretical risk and the difference between coincidence and
causation. Once you raise the notion of a possibility of harm, he
says, ‘‘it’s hard for people to get that notion out of their head.’’
Kaufman thinks the problem is more immediate than bridging
the gap between lay and expert understanding of risk. Parents
treated theoretical risk as fact even as scientists tested, and
ultimately rejected, the possibility that thimerosal might harm
children. Thinking the institutions that were supposed to protect
them from risk failed, Kaufman says, people now do their own
research. But instead of leading to more certainty, she explains,
‘‘collecting more information actually increases doubt.’’
With the explosion of ‘‘contrary’’ expertise online, Kaufman
says, ‘‘many parents see even the most respected vaccine experts’
perspective on the issue as just one more opinion.’’ The bulk of
antivaccination Web sites present themselves as legitimate sources
of scientific information, using pseudoscientific claims and
emotional appeals, according to a 2002 study in Archives of Disease
in Childhood . Making matters worse, the study found, nearly all
sites adopted an ‘‘us versus them’’ approach, casting doctors and
scientists as either ‘‘willing conspirators cashing in on the vaccine
‘fraud’ or pawns of a shadowy vaccine combine.’’ Parents’ intuitive
views about vaccines were elevated above ‘‘cold, analytical
science.’’ Accounts of children ‘‘maimed or killed by vaccines’’
were common—a finding that may help explain why those who
advocate immunization receive death threats.
And scientists on TV and radio are hard-pressed to compete
with the emotional appeals of activists. It doesn’t help that science
can’t provide what some parents are looking for: the definitive
study to prove that vaccines did not cause their child’s autism.
‘‘You can never say a theory’s been completely disproved, but
that’s just the nature of science,’’ observes Baron-Cohen. ‘‘So for
parents, that provides something to hold on to, gives hope that the
theory might one day be supported.’’
As well-organized groups exploit hope and fear, parents
wondering about vaccines share the fruits of their online
investigations—and doubts—with moms’ groups, listservs, chat
rooms, and friends. Even parents who ultimately decide to
vaccinate, Kaufman says, ‘‘only feel safe if they’re on some sort
of schedule that isn’t set by science.’’ ‘‘Dr. Bob’’ Sears wrote a
book that gives parents a formula to delay, withhold, separate, or
space out their vaccines: The Vaccine Book: Making the Right Decision
for Your Child sold over 100,000 copies in just two years.
These untested, ‘‘made-up’’ schedules just increase the window
of risk for children by exposing them to potentially deadly vaccine-
preventable diseases with no benefit, warns Offit. Though overall
vaccination rates in the US are high, vaccine-resistant communi-
ties like Ashland have emerged in several states, including
Colorado, Washington, and California, as more parents adopt
alternative schedules or seek exemptions to avoid vaccination.
Recent studies have shown that exempt children in Colorado were
22 times more likely to contract measles and about 6 times more
likely than vaccinated children to contract pertussis, while exempt
children nationwide were 35 times more likely than vaccinated
children to contract measles .
Sadly, studies suggest that the burden of lowered immunization
rates will likely fall disproportionately on poor people living in
crowded conditions, hotbeds of disease transmission, and exacer-
bate existing health disparities among minority populations—where
kids go unvaccinated not by choice but because of limited access to
health services. Exemptions also pose a threat to children who can’t
be vaccinated because of a medical condition or who didn’t mount
an immune response to the vaccine, as well as to hundreds of
thousands of people on chemotherapy, recovering from organ
transplants, or struggling with compromised immunity.
Information technology has transformed the way trust and
knowledge are produced, Kaufman says: ‘‘Scientists have to
consider their role in this changed landscape and how to compete
with these other sources of knowledge.’’ As science chips away at
the genetic sources of this collection of conditions we call autism,
she adds, it will chip away at the idea of a connection between
vaccines and autism.
Until researchers get a better handle on the causes of autism,
Baker thinks scientists need to find a way to make dry scientific
results as compelling as anecdotal case studies. The studies that are
‘‘most elegant to a scientist,’’ he says, are just much harder for most
parents to understand than what happens to an individual child.
Rachel Casiday, a medical anthropologist at the Centre for
Integrated Health Care Research at Durham University, UK, who
studied British parents’ attitudes toward MMR, says scientists
should not underestimate the importance of narrative. People
relate much more to a dramatic story—‘‘he got his vaccination, he
stopped interacting, and he hasn’t been the same since’’—than
they do to facts, risk analyses, and statistical studies. ‘‘If you
discount these stories, people think you have an ulterior motive or
you’re not taking them seriously,’’ she explains. Casiday suggests
providing an alternative, science-based explanation or relating
emotionally compelling tales about counter-risk—such as help-
lessly watching a young child die of a vaccine-preventable
disease—in the same narrative format.
McCarthy emerged as a hero for some parents by telling her
story. Personal stories resonate most with those who see trust in
experts as a risk in itself—a possibility whenever people must
grapple with science-based decisions that affect them, whether
they’re asked to make sacrifices to help curb global warming or
vaccinate their kids for public health. Researchers might consider
taking a page out of the hero’s handbook by embracing the power
of stories—that is, adding a bit of drama—to show that even
though scientists can’t say just what causes autism or how to
prevent it, the evidence tells us not to blame vaccines. As news of
epidemics spreads along with newly unfettered infectious diseases,
those clinging to doubt about vaccines may come to realize that
several potentially deadly diseases are just a plane ride, or
playground, away—and that vaccines really do save lives.
PLoS Biology | www.plosbiology.org6May 2009 | Volume 7 | Issue 5 | e1000114
References and Further Reading
1. Wakefield A, Murch S, Anthony A, Linnell J, Casson DM, et al. (1998) Ileal-
lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental
disorder in children. Lancet 351: 637–641. doi:10.1016/S0140-6736(97)11096-
2. General Medical Council, UK. Available: http://www.gmc-uk.org. Accessed 20
3. Institute of Medicine (2004) Immunization safety review: Vaccines and autism.
Washington (DC): National Academies Press, 31. Available: http://www.nap.
edu/catalog.php?record_id=10997. Accessed 20 April 2009.
4. Institute of Medicine. Immunization safety review: Vaccines and autism.
Available: http://www.iom.edu/CMS/3793/4705/20155.aspx. Accessed 20
5. Verstraeten T, Davis RL, DeStefano F, Lieu TA, Rhodes PH, et al. (2003)
Safety of thimerosal-containing vaccines: a two-phased study of computerized
health maintenance organization databases. Pediatrics 112: 1039–1048.
6. VaccineInfo.net (2004) Parent groups denounce IOM report refuting vaccine
autism connection. Available: http://www.vaccineinfo.net/releases/IOM_
vaccine_autism_report.htm. Accessed 20 April 2009.
7. Florida Institute of Technology new release. Available: http://www.fit.edu/
newsroom/brief.html?id=2396. Accessed 20 April 2009.
8. Hargreaves I, Lewis J, Speers T (2003) Towards a better map: Science, the
public and the media. Economic and Social Research Council. Available:
http://www.comminit.com/en/node/177710. Accessed 20 April 2009.
9. NHS Information Centre. Available: http://www.ic.nhs.uk/statistics-and-data-
2007-08-%5Bns%5D. Accessed 20 April 2009.
10. Kaufman SR (2007) An event in the history of thought: Autism and vaccine
safety doubt. Paper presented at the American Anthropological Association
conference, Washington, DC November.
11. US Food and Drug Administration. Frequently asked questions. Available:
http://www.fda.gov/cber/vaccine/thimfaq.htm#q5. Accessed 20 April 2009.
12. American Academy of Pediatrics (1999) Thimerosal in vaccines—an interim
report to clinicians. AAP News 15: 10.
13. Halsey NA (1999) Limiting infant exposure to thimerosal in vaccines and other
sources of mercury. JAMA 282: 1763–1766.
14. Bernard S, Enayati A, Redwood L, Roger H, Binstock T (2001) Autism: a novel
form of mercury poisoning. Med Hypotheses 56: 462–471.
15. Baker J (2008) Mercury, vaccines, and autism: One controversy, three histories.
Am J Public Health 9: 244–253.
16. Wallinga J, Heijne JCM, Kretzschmar M (2005) A measles epidemic threshold
in a highly vaccinated population. PLoS Med 2(11): e316. doi:10.1371/
17. Poling JS, Frye RE, Shoffner J, Zimmerman AW (2006) Developmental
regression and mitochondrial dysfunction in a child with autism. J Child Neurol
18. Frye RE, Zimmerman AW, Shoffner JM (2008) Conflict of interest statement
concerning ‘‘Developmental regression and mitochondrial dysfunction in a child
with autism’’ J Child Neurol 23: 1089–1090.
19. Davies P, Chapman S, Leask J (2002) Antivaccination activists on the world wide
web Arch Dis Child 87: 22–25.
20. Feikin DR, Lezotte DC, Hamman RF, Salmon DA, Chen RT (2000) Individual
and community risks of measles and pertussis associated with personal
exemptions to immunizations, JAMA 284: 3145–3150.
21. National Institute of Neurological Disorders and Stroke. Autism Fact Sheet.
htm#133883082. Accessed 20 April 2009.
22. Baron-Cohen S (2008) Autism - in 100 words. Br J Psychiatr 193: 321.
23. Auyeung B, Baron-Cohen S, Ashwin E, Knickmeyer R, Taylor K, et al. (2009)
Fetal testosterone and autistic traits. Br J Psychol 100: 1–22.
PLoS Biology | www.plosbiology.org7 May 2009 | Volume 7 | Issue 5 | e1000114