The “Why Vaccines Don’t Cause Autism” Papers
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.
- Jain A, Marshall J, Buikema A, Bancroft T, Kelly JP, Newschaffer CJ (2015) Autism occurrence by MMR vaccine status among US children with older siblings with and without autism. JAMA 313(15): 1534–40. doi: 10.1001/jama.2015.3077. pmid:25898051
- Uno Y, Uchiyama T, Kurosawa M, Aleksic B, Ozaki N (2015) Early exposure to the combined measles-mumps-rubella vaccine and thimerosal-containing vaccines and risk of autism spectrum disorder. Vaccine 33(21):2511–6. doi: 10.1016/j.vaccine.2014.12.036. pmid:25562790
- Taylor LE, Swerdfeger AL, Eslick GD (2014) Vaccines are not associated with autism: an evidence-based meta-analysis of case-control and cohort studies. Vaccine 2014; 32(29): 3623–9. doi: 10.1016/j.vaccine.2014.04.085. pmid:24814559.
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:
- Zerbo O, Qian Y, Yoshida C, Fireman BH, Klein NP, Croen LA (2017) Association Between Influenza Infection and Vaccination During Pregnancy and Risk of Autism Spectrum Disorder. JAMA Pediatr. 2017 Jan 2;171(1):e163609. doi: 10.1001/jamapediatrics.2016.3609.
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.
I would be interested to know if you’ve watched the documentary “Vaxxed” and what your take is on it.
Thank you for your work. My son, Aaron, died in 1994 from complications of the chicken pox. Aaron died 21 days after his first pox mark. He had three surgeries. His aorta burst when they thought he was getting better. The autopsy showed that he had developed Group A Strep. As you know, the vaccine was approved in the USA in 1995. I don’t know why so many people are fighting vaccines. Our other boys have had all the recommended vaccinations and Boosters.
The PDF link to the 21 page list of papers compiled by the American Academy of Pediatrics doesn’t work. Can it be corrected or am I being punished for not having an account there or paying for it? If it’s behind a pay wall it has to come out because that’s how the propaganda merchants are winning the information war.
Thanks Peter, this is a great addendum to the existing body of evidence. The challenges just seem to get worse every year with such spurious justifications offered by parents.
Recommended reading for non-scientists: a book that tells the whole story about vaccines and autism and how this theory was debunked multiple times : “The panic virus” by Seth Mnookin. EXCELLENT historical account!!
All studies have flaws. However, the Jain Jama (2015) study http://jamanetwork.com/journals/jama/fullarticle/2275444 has some significant design flaws that cannot be ignored.
This study used Optum’s private insurance claims database to do a retrospective analysis. There are many flaws in this study’s design. 1) The data is not stratified to look at children with a comorbid gastrointestinal diagnosis. It is the children with gastrointestinal disease and ASD that it is theorized are more likely to have had the MMR vaccine play a role in developing autism. 2) It did not take race and age of MMR vaccination into account. Receiving the MMR before 3 years of age puts a child at increased risk. Black boys under 3 also have a 3 fold increased risk (at least that is what the preliminary data said according to William Thompson regarding his 2004 Pediatrics study). In fact, this Jama 2015 study specifically says that its sample underrepresents the minority population. 3) This study findings did not account for the fact that a significant number of children with autism diagnoses would not even be in the private claims database. Depending on one’s state, children under 3 receive services through Early Intervention and parents can choose not to have their private insurer notified. It’s mentioned in discussion. And many of the providers parents may see may not accept insurance. Filing a claim would depend on their out of network coverage. 4) The study used an algorithm to determine an ASD diagnosis. I would be interested to see the results of this data if it used a different or an additional data source to validate ASD diagnosis. 5) The average age of ASD diagnosis isn’t until 4 years old. And, while the study looked at an 11 year period, it also tried to look at ASD in siblings so the time frame may not be long enough.
While the Autism spectrum is wide, the findings of this poorly designed study cannot be taken as definitive proof that there is no causal relationship in some cases.
Thank you Dr Hoetz. This is a marvelous post. Sharing everywhere.
Thank you for commenting. We suggest that you also post these comments to PubMed Commons (https://www.ncbi.nlm.nih.gov/pubmedcommons/), where the authors of this study can be notified and given the opportunity to respond.
Thank you for this comment. We suggest you read the Public Health Perspectives response to “Vaxxed”, which includes comments from Dr. Hotez:
Thank you for noticing this. We’ve fixed the link.
“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.”
Indeed, one of the known causes of autism is rubella infection (NOT vacination) in the first trimester of pregnancy. This being the case, MMR vaccine (by protecting pregnant women both directly and indirectly) prevents (some cases of) autism.