Pro Vaccine Research Paper

Four vaccine myths and where they came from

By Lindzi Wessel

False: Vaccination can cause autism

In 1998, U.K. doctor Andrew Wakefield published a study in The Lancet suggesting that the measles, mumps, and rubella (MMR) vaccine could trigger autism. In the years after, MMR vaccination rates among 2-year-olds in England dropped below 80%. But the claim began to unravel in 2004 after journalist Brian Deer reported undisclosed conflicts of interest: Wakefield had applied for a patent on his own measles vaccine and had received money from a lawyer trying to sue companies making the MMR vaccine. Citing further concerns about ethics and misrepresentation, The Lancet retracted the paper in 2010. Shortly after, the United Kingdom's General Medical Council permanently pulled Wakefield's medical license.

But the MMR-autism falsehood made headlines again in 2016 with the release of Vaxxed, a movie Wakefield directed that alleges a cover-up by the Centers for Disease Control and Prevention (CDC). The story features bioengineer Brian Hooker, who took issue with a 2004 CDC study that found no overall difference in vaccination rates between kids with and without autism. Hooker reanalyzed the data in 2014 and claimed CDC had hidden evidence that the vaccine could increase autism risk in black boys. In fact, CDC noted in the paper that rates of vaccination in the oldest age group were slightly higher in kids with autism. But CDC says that this effect was "most likely a result of immunization requirements for preschool special education program attendance in children with autism."

Such claims prompted a slew of studies finding no evidence that MMR causes autism. For example, a 2014 meta-analysis in Vaccine examined studies involving a total of almost 1.3 million people. That same year, a paper in the Journal of the American Medical Association reported that no difference existed in autism rates between thousands of vaccinated and unvaccinated children.

False: Mercury in vaccines acts as a neurotoxin

In 2005 the magazines Rolling Stone and Salon copublished a story by environmental lawyer Robert F. Kennedy Jr. (nephew of former President John F. Kennedy) alleging a government conspiracy to cover up evidence that thimerosal, a mercury-containing preservative once used in vaccines, can cause brain problems, including autism. Multiple corrections soon appeared, including one noting that Kennedy had incorrectly stated the mercury levels. In 2011 Salon retracted and removed the story, noting "continued revelations of the flaws and even fraud tainting the science behind the connection."

Kennedy has continued to use his name to promote the idea, and in recent months vaccine skeptics have called for a new "vaccine safety" commission with Kennedy at its head. Yet according to the Centers for Disease Control and Prevention (CDC) in Atlanta and the World Health Organization, no evidence exists that thimerosal from vaccines causes health problems in kids.

In 2001, well before Kennedy's article or his related book, thimerosal was removed from all childhood vaccines in the United States except multidose vials of flu vaccine. "If it did cause autism, the prediction would be that once thimerosal was taken out of vaccines that then the numbers of cases of autism should have leveled off or gone down. But that did not happen," says Frank DeStefano, director of CDC's Immunization Safety Office. A rumor that autism incidence dropped in Denmark after it removed thimerosal in 1992 also is not true. The rumor apparently arose from a misinterpretation of epidemiological data.

False: Countering mercury from vaccines can make children better

In the mid-2000s, riding the wave of concerns about thimerosal, a mercury-containing preservative, Maryland doctor Mark Geier and his son, David, began to promote a theory that a pathological interaction between mercury and testosterone explained many symptoms of autism. That claim came after the Geiers published a few studies suggesting a link between thimerosal and autism—studies that the Institute of Medicine characterized as having "serious methodological flaws." Despite that review, the Geiers proceeded with their controversial work. They established an unapproved treatment that involved daily injections of leuprolide (Lupron) , a drug used to treat prostate cancer and to chemically castrate sex offenders. In children, the drug is approved only to treat precocious puberty, a rare condition in which puberty begins before the age of 8 years. Side effects in kids can include bone and heart damage. Leuprolide also carries a risk of exacerbating seizure disorders, a condition commonly associated with autism. The Geiers sometimes paired those injections with chemical chelation, a risky treatment for patients with heavy metal poisoning. To peddle their treatments to parents and insurance companies at a cost upward of $5000 a month, the Geiers improperly diagnosed children with precocious puberty—without performing the necessary diagnostic tests. They also misled parents into believing that the regimen was approved to treat autism, according to a 2011 investigation by the Maryland Board of Physicians. The board revoked Mark Geier's state medical license, saying his practice "far exceeds his qualifications and expertise," and other states followed suit. His son, who holds only a Bachelor of Arts degree, was charged with practicing medicine without a license.

False: Spreading out vaccines can be safer for kids

Some vaccine skeptics contend that the Centers for Disease Control and Prevention's (CDC's) current vaccination schedule, which protects children from 14 diseases before age 2, requires too many vaccines in too short a time—overloading children's immune systems early in life. That overload, the skeptics argue, leaves children prone to a host of disorders, including neurodevelopmental delays and diabetes. Experts roundly dismiss those claims. A child's immune system must cope with thousands of foreign antigens each day, whereas the 2014 recommended vaccine schedule exposes a child to only about 300 antigens by the age of 2, according to CDC. One estimate, by vaccine expert Paul Offit of the Children's Hospital of Philadelphia in Pennsylvania, suggests 11 vaccines given to an infant at one time would temporarily "use up" only 0.1% of the child's immune system. And although the number of recommended vaccines has risen over the years, advances in vaccine development mean that the number of antigens contained in those vaccines has decreased—yet rates of autism and diabetes have not.

In a 2015 survey of 534 pediatricians and family doctors published in the journal Pediatrics, only about 1% agreed that vaccines should be spread out. But almost all of them had sometimes given in to parent requests to do so, and some doctors have published "alternative" vaccination schedules. But alternative schedules pose many problems, Offit says. The most obvious is that extending the schedule leaves children vulnerable to dangerous diseases for longer. Spacing out vaccinations also makes it more likely that kids will not get all their shots. One proposed alternative schedule would require 19 doctor visits over 6 years—12 of those by age 2. Requiring more visits increases the burden on parents and could expose children to more illnesses from sick patients in waiting rooms, Offit says.


More from News

PLOS NTDs co-Editor-in-Chief Peter Hotez lists the key scientific papers refuting the myth that vaccines cause autism

I have a unique perspective on the recent headlines surrounding vaccines and their alleged links to autism. I serve as President of the Sabin Vaccine Institute, a non-profit organization devoted to vaccines and immunization. In that role I am director of its product development partnership (PDP) based at Baylor College of Medicine – the Sabin Vaccine Institute and Texas Children’s Hospital Center for Vaccine Development, which makes vaccines for neglected tropical diseases – a group of poverty-promoting parasitic and related infections – including new vaccines for schistosomiasis, Chagas disease, and leishmaniasis, among others.

But I’m also a father of four children, including my adult daughter Rachel who has autism and other mental disabilities. These two parts of my life place me at an interesting nexus in a national discussion of autism and vaccines. My position is firm: there is no link and I also believe there is no plausibility to such a link. My position is mostly based on the scientific literature, together with my perspective as an autism father witnessing first-hand the impact of this condition on Rachel and our family.



Regarding the scientific literature, I thought it might be helpful to share with the community of interested individuals, the major peer-reviewed articles I consult regularly to back up my pro-vaccine sentiments and position. These are the papers I often cite when speaking with journalists and other interested individuals. Together they refute allegations that autism is linked to vaccination, including:

  • the MMR vaccine,
  • trace thimerosal used in some vaccines,
  • the close spacing of vaccines.


Papers refuting links between childhood vaccines and autism

First, are the recent studies (involving hundreds of thousands of children) showing no link and cited in my recent PLOS Medicine paper that predicts Texas will soon have measles epidemics due to widespread non-medical exemptions: The papers refute both the MMR vaccine and thimerosal as having any role in autism.

The three epidemiological studies are the newest ones in addition to the 21 page list of papers compiled by the American Academy of Pediatrics (AAP) (pdf here).


Paper refuting link between maternal immunization and autism

With regards to maternal immunization there is a new 2017 JAMA Pediatrics article showing that maternal influenza immunization also has no impact on autism:

Non-human primate study

Beyond these epidemiological studies, are the important non-human primate experimental studies published in the Proceedings of the National Academy of Sciences USA showing that the infant vaccine series does not produce either autism-like behavior or neuropathology:

  • Gadad BS, Li W, Yazdani U, Grady S, Johnson T, Hammond J, Gunn H, Curtis B, English C, Yutuc V, Ferrier C, Sackett GP, Marti CN, Young K, Hewitson L, German DC. Administration ofthimerosal-containing vaccines to infant rhesus macaques does not result in autism-like behavior or neuropathology. Proc Natl Acad Sci U S A. 2015 Oct 6;112(40):12498-503

According to the paper summary: “Here we gave nonhuman primate infants similar vaccines given to human infants to determine whether the animals exhibited behavioral and/or neuropathological changes characteristic of autism. No behavioral changes were observed in the vaccinated animals, nor were there neuropathological changes in the cerebellum, hippocampus, or amygdala. This study does not support the hypothesis that thimerosal-containing vaccines and/or the MMR vaccine play a role in the etiology of autism”.

Taken together these studies show that childhood or maternal vaccines do not cause autism.


Absence of plausibility

I also point out that the lack of plausibility of any link between childhood vaccines and autism. Numerous studies indicate that autism is associated with changes neocortex of the brain in early pregnancy well before a child receives vaccines. The data are nicely presented in this New England Journal of Medicine article by Eric Courchesne’s group at the University of California San Diego:

  • Stoner R, Chow ML, Boyle MP, Sunkin SM, Mouton PR, Roy S, Wynshaw-Boris A, Colamarino SA, Lein ES, Courchesne Patches of disorganization in the neocortex of children with autism. N Engl J Med. 2014 Mar 27;370(13):1209-19. doi: 10.1056/NEJMoa1307491.

Such studies, showing profound changes in the reorganization of the brain strongly reinforce the genetic and epigenetic basis of autism.   A vaccine simply could not do this, and the data supports this.

Instead, there are a lot of exciting studies identifying new genes and epigenetics linked to autism. For example, this excellent overview in Nature Neuroscience. My position is that if there is also any environmental component to autism, it would have to be something that occurs early around the time of conception or in the first trimester of pregnancy. The major vaccine given in pregnancy regularly is flu vaccine, but as the paper in JAMA Pediatrics points out there is no link.

From my perspective the antivaxxer movement is growing in strength and momentum. In order to counter allegations that vaccines could cause autism, it is both useful and informative to have access to some key recent scientific literature.


Prof. Peter Hotez MD PhD is professor of pediatrics and molecular virology and microbiology at Baylor College of Medicine, where is also Texas Children’s Hospital Endowed Chair in Tropical Pediatrics, and Dean of the National School of Tropical Medicine. He is also the President of the Sabin Vaccine Institute and director of the Texas Children’s Hospital Center for Vaccine Development.


Featured Image Credit: ZaldyImg, Flickr

This post was edited to fix the broken link to the AAP list and a typo in the last sentence.


Leave a Reply

Your email address will not be published. Required fields are marked *