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What is VAERS and what does it do?

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Common Questions-girl getting vaccinated at doctor's office

The Vaccine Adverse Event Reporting System, or VAERS, is a vaccine safety monitoring system and part of the national vaccine safety net. VAERS accepts and analyzes reports of possible health problems that people have after they get vaccinated. Anyone can submit a report to VAERS, and VAERS reports are available to the public. The U.S. Centers for Disease Control and Prevention (CDC) and the U.S. Food and Drug Administration (FDA) use VAERS to help identify potential safety problems with vaccines.source: 1

There are some important things to know about VAERS:

  • VAERS is an important part of the vaccine safety net. VAERS is one of several systems that work together to monitor vaccine safety. The role of VAERS is to collect information about issues that are reported to have happened after someone received a vaccine so that vaccine experts can identify any potential safety problems that should be further analyzed.source: 1
  • Anyone can report what they think could be a vaccine-related adverse event to VAERS.source: 1 Patients, parents, caregivers, and health care providers can report adverse events after vaccination even if they are not sure that the vaccine caused the adverse event. In addition, health care providers are required to report certain types of adverse events after vaccination, such as allergic reactions and deaths.source: 2 
  • A VAERS report does not necessarily mean something was caused by the vaccine. VAERS is a way to collect information and identify unusual, previously unreported adverse events, or unexpected patterns that may be related to vaccinations. But just because an event happened after a vaccination doesn’t necessarily mean the event happened because of the vaccine. That’s why potential safety problems reported to VAERS need to be evaluated by experts to find out whether those safety problem are related to a vaccine.source: 2

Key Evidence

  • VAERS is important but has limitations.source: 3 Because VAERS is a data collection system, it cannot, by itself, determine whether an adverse event is related to a vaccine.source: 4 Anyone can report to VAERS, which is part of why it is such a robust system. But that also means that some reports may have incomplete, inaccurate, or false information.source: 5
  • Correlation does not equal causation. When it comes to health and medicine, it’s sometimes hard to understand the difference between correlation and causation. Causation means one thing caused the other. Correlation means that two things happen around the same time. An example of correlation and causation is when a dog barks before a bolt of lightning in the sky, then a clap of thunder can be heard. The dog did not cause the thunder, it just happened to bark around the same time. However, the bolt of lightning did cause the noise of thunder. VAERS reports correlations—things that happen around the same time as a vaccine being given. But VAERS does not determine causation, which is when the issue being reported was caused by vaccines.source: 3 Rather, researchers use proven analytic safety systems and processes that can best determine whether the vaccine caused a safety issue.source: 6
  • VAERS is just one part of the safety system. VAERS works with other safety systems to identify potential problems so that vaccine experts can research the issue.source: 6 Other parts of the safety system work with health care organizations and medical centers to monitor vaccines and conduct vaccine safety research. Combined, these systems provide a very strong safety net.source: 7
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Common Questions-boy at doctor's office

A Deeper Dive: VAERS and vaccine misinformation

People opposed to vaccines often use VAERS as part of their efforts to “prove” vaccine safety issues. But it is a system that only collects reports, rather than researching or analyzing them; a VAERS report alone does not prove anything.source: 3 It is important to understand what VAERS can and can’t do, so you can better identify misinformation. Misinformation can be dangerous. Here are some examples of how VAERS data have been misused in the past:source: 8

  • Making assumptions. For example, a group identified vaccine lots that had the most reports associated with them and labeled the vaccine doses from these lots as toxic. But vaccine lots vary in size. It’s totally normal for a 100,000-dose vaccine lot to have more VAERS reports than a lot containing 3,000 vaccine doses.
  • Assuming causality. Organizations and individuals opposed to vaccines use VAERS reports to say a bad thing that happened is because of a vaccine. Someone may report that a person died after being vaccinated but upon investigation, it may turn out that the person died from an existing disease like diabetes or in a car accident. The vaccine had nothing to do with the death—they just happened around the same time.
  • Assuming all VAERS reports are true and serious. Most VAERS reports are about adverse events that are not considered serious. That’s because most VAERS reports are about known and minor side effects. So a vaccine may have a lot of reports but that does not mean the vaccine is unsafe. Rather, it means the something happened after a vaccine was given. Serious reactions to a vaccine are rare, but an unexpected medical issue is more likely to be reported than a minor one, even if it is not related to the vaccine.source: 7 When a serious report is made, the VAERS staff follows up to get medical information to understand what happened. It is also important to acknowledge that, on occasion, people file reports that are not true.source: 6 A VAERS report alone does not prove anything.source: 3 The system was made to make it easy for people to submit a report, but it also means that false reports are sometimes submitted.source: 2 Here’s an example: A doctor once submitted a report claiming he turned into the Incredible Hulk after getting a vaccine. Of course, it was totally false, but he submitted the report to prove the point. If he hadn’t removed the report himself, it would still be in the VAERS database today. The occasional false report does not mean VAERS doesn’t work. It works extremely well in identifying potentially serious issues; it just doesn’t evaluate them.source: 2 Other systems and scientific and medical experts determine whether issues found in VAERS are possibly related to vaccines.source: 6

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More information

Still have questions? Talk to your child's doctor, nurse, or pharmacist.

Sources

  1. HHS: About VAERS
  2. HHS: VAERS FAQ
  3. HHS: Guide to Interpreting VAERS Data
  4. FDA: Vaccines Protect Children From Harmful Infectious Diseases
  5. CDC: 10 Things Health care Providers Need to Know about the Vaccine Adverse Event Reporting System
  6. HHS: VAERS Data
  7. CDC: How Vaccine Safety Monitoring Works
  8. FactCheck.org: What VAERS Can and Can’t Do, and How Anti-Vaccination Groups Habitually Misuse Its Data
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