Are vaccines safe?

You may have seen that the wording on a major public health webpage about vaccines and autism was updated in late 2025. As clinicians who spend our lives caring for children, we found the new phrasing concerning. It has already caused confusion, and some parents may understandably wonder what it means.

We wanted to take a moment to explain why this matters and how we think about it as pediatric experts.

Imagine someone says, "Prove that unicorns don't exist."

To truly prove that statement, you would have to search everywhere, across all of history.

Even after searching and finding nothing, someone could still say, "Well, maybe you just haven't looked in the right spot yet."

It's an impossible standard.

Vaccine science research

Science doesn't operate by "proving a negative."

Instead, it looks for evidence. If we search thoroughly and consistently, and all the evidence continues to show nothing, then the most reasonable conclusion is that the thing we're looking for simply isn't there.

That's exactly what has been done with vaccines and autism. For more than 25 years, scientists and doctors around the world have studied this question from every angle:

  • Research involving millions of children
  • Studies done in multiple countries
  • Comparisons of vaccinated and unvaccinated children
  • Reviews of every major childhood vaccine
  • Careful evaluation of ingredients like thimerosal
  • Independent studies by experts in pediatrics, neurology, epidemiology, and public health

Across all of this research, the conclusion has been the same, again and again:

Vaccines do not cause autism.

There's no pattern, no trend, no sign, and no reliable evidence of a connection.

This is very different from the article that was published in the late 1990s that sparked all the confusion about vaccines and autism.

This claim of a connection came from a small, flawed study involving only 12 children that was later shown to contain serious errors and bias.

  • The article was officially retracted due to multiple investigations confirming that the conclusions were invalid.
  • The journal published an official apology for the negative impact caused by publishing the claims now proven to be false.
  • The author was found guilty of professional misconduct related to the study, and their medical license was revoked.

Modern research has also repeatedly shown those claims were incorrect.

Parents deserve clear, honest information, especially at a time when misinformation spreads so quickly. We know that when families come to us with questions, it is because they want to protect their children.

Vaccine research microscopy

The good news is that vaccine safety is monitored more closely than almost any other medical intervention.

Vaccines are given to healthy children, which means the bar for safety is extraordinarily high, in many ways higher, than it is for medicines used to treat people who are already ill.

There are multiple national and international systems that constantly monitor vaccine safety.

These systems work together to catch even extremely rare safety concerns and they have not found a link between vaccines and autism.

VAERS (Vaccine Adverse Event Reporting System)

A U.S. system that collects reports of possible side effects so experts can look for patterns.

VSD (Vaccine Safety Datalink)

A collaborative effort involving a national public health agency and large health systems, leveraging electronic health records to study vaccine outcomes in real time.

CISA (Clinical Immunization Safety Assessment Project)

A network of vaccine experts that evaluates rare or unusual reactions.

WHO (Global Advisory Committee on Vaccine Safety)

An international body reviewing data from countries around the world.

We also want to acknowledge something important that should not get lost in this discussion on vaccines:

Autism is real,

and receiving a new diagnosis can feel overwhelming for many families.

Parents may worry about what it means for their child's future, their education, or their daily lives. These feelings are normal, and the questions are important to get answered.

Autism is not caused by vaccines, but it is something that many families navigate with courage, love, and resilience. Early support can make a meaningful difference, and there are excellent resources available:

  • Autism Speaks
    Parent Support and Resource Guide
  • The Autism Society
    Local chapters offering support groups, education, and community connections
  • Local Early Intervention Programs
    State-specific: contact your medical provider for help finding these resources
  • School-based services and evaluations through the public school system

Every child with autism is unique, and with the right supports, children often thrive socially, academically, and emotionally. If you have concerns about your child's development or a new diagnosis, we are here to guide and support you.

Sources & Further Reading

1. The original, flawed study

Wakefield, A.J., et al. (1998). Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorders in children. The Lancet, 351(9103), 637–641.

  • Note: This was the paper that first suggested a link between the MMR vaccine and autism. It involved only 12 children, used poor methods, omitted key information, and was funded by attorneys involved in vaccine litigation.

2. What happened to the Wakefield study?

Retraction Notice — The Lancet (2010).

  • The Lancet fully retracted the Wakefield paper, stating that key elements were found to be "false" and the findings were unreliable.

UK General Medical Council (GMC) Ruling (2010).

  • Found Wakefield guilty of serious professional misconduct, including unethical treatment of children and undisclosed financial conflicts of interest.
  • His medical license was revoked.

3. Major studies showing no link between vaccines and autism

Large Population and Cohort Studies:

Andersen, A.-M. N., et al. (2019). Measles, Mumps, Rubella Vaccination and Autism: A Nationwide Cohort Study. Annals of Internal Medicine, 170(8), 513–520.

  • 650,000+ children in Denmark
  • Conclusion: No autism risk from MMR

Hviid, A., et al. (2002). Association Between Thimerosal-Containing Vaccine and Autism. JAMA, 290(13), 1763–1766.

  • Large national dataset
  • Conclusion: No association

Madsen, K. M., et al. (2002). A Population-Based Study of MMR Vaccination and Autism. NEJM, 347(19), 1477–1482.

  • Over half a million children
  • Conclusion: No link
U.S. and International Studies

DeStefano, F., et al. (2013). Exposure to Antibody-Stimulating Proteins and Autism Risk. Pediatrics, 131(4), 604–659.

  • Examined total vaccine exposure
  • Conclusion: No association

Taylor, L. E., et al. (2014). Vaccines Are Not Associated with Autism: Meta-analysis. Vaccine, 32(29), 3623–3629.

  • Over 1.2 million children
  • Conclusion: No relationship

Price, C. S., et al. (2010). Prenatal and Infant Thimerosal Exposure and Autism. Pediatrics, 126(4), 656–664.

  • Public health–led study
  • Conclusion: No increased risk
Reviews by Major Health Organizations

Institute of Medicine (2001, 2004).

  • Reviewed all major evidence
  • Conclusion: No causal link

World Health Organization (WHO).

  • Ongoing global surveillance
  • Conclusion: No link between vaccines and autism

Get in touch

VaxFacts is a trusted online resource, meticulously compiled by a network of nationally respected pediatricians. It serves as a reliable source for comprehensive and evidence-based vaccine information in the U.S.