Vaccine Adverse Event Reporting System (VAERS)
As of March 24, 2021, there are three COVID-19 vaccines available for use in the United States under Emergency Use Authorization (EUA). These vaccines are monitored by VAERS and several other vaccine safety monitoring systems as part of the most intensive vaccine safety monitoring effort in U.S. history. This continuous, robust safety monitoring helps keep COVID-19 vaccines safe and helps ensure the benefits of vaccination continue to outweigh any risks.
Learn more about Ensuring COVID-19 Vaccine Safety in the U.S.
Healthcare providers are required to report certain adverse events following COVID-19 vaccination to VAERS. Learn about COVID-19 vaccine EUA reporting requirements for healthcare providersexternal icon.
VAERS is the nation’s early warning system that monitors the safety of vaccines after they are authorized or licensed for use by the U.S. Food and Drug Administration (FDA). VAERS is part of the larger vaccine safety system in the United States that helps make sure vaccines are safe. The system is co-managed by CDC and FDA.
VAERS accepts and analyzes reports of possible health problems—also called “adverse events”—after vaccination. As an early warning system, VAERS cannot prove that a vaccine caused a problem. Specifically, a report to VAERS does not mean that a vaccine caused an adverse event. But VAERS can give CDC and FDA important information. If it looks as though a vaccine might be causing a problem, FDA and CDC will investigate further and take action if needed.
Anyone can submit a report to VAERS — healthcare professionals, vaccine manufacturers, and the general public. VAERS welcomes all reports, regardless of seriousness, and regardless of how likely the vaccine may have been to have caused the adverse event.
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VAERS is a national vaccine safety surveillance program that helps to detect unusual or unexpected reporting patterns of adverse events for vaccines.
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VAERS accepts reports from anyone, including patients, family members, healthcare providers and vaccine manufacturers.
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VAERS is not designed to determine if a vaccine caused or contributed to an adverse event. A report to VAERS does not mean the vaccine caused the event.
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VAERS is a passive surveillance system, meaning it relies on people sending in reports of their experiences after vaccination.
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Healthcare providers and vaccine manufacturers are required by law to report certain events after vaccination.
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If VAERS detects a pattern of adverse events following vaccination, other vaccine safety monitoring systems conduct follow up studies.
Anyone can submit a report to VAERS. Learn more about which adverse events to report and how to report them.
VAERS is part of the larger post-licensure vaccine safety monitoring system in the United States. After vaccines are licensed or authorized for use by FDA, they are continually monitored for safety by multiple, complementary systems. These systems also conduct safety studies in populations that are larger and more diverse than those typically included in vaccine clinical trials.
As a passive reporting system, VAERS relies on individuals to send in reports of adverse health events following vaccination. From these reports, VAERS scientists can:
- Assess the safety of newly licensed vaccines
- Detect new, unusual, or rare adverse events that happen after vaccination
- Monitor increases in known side effects, like arm soreness where a shot was given
- Identify potential patient risk factors for particular types of health problems related to vaccines
- Identify and address possible reporting clusters
- Recognize persistent safe-use problems and administration errors
- Watch for unexpected or unusual patterns in adverse event reports
- Serve as a monitoring system in public health emergencies
The information collected by VAERS can quickly provide an early warning of a potential safety problem with a vaccine. Patterns of adverse events, or an unusually high number of adverse events reported after a particular vaccine, are called “signals.” If a signal is identified through VAERS, scientist may conduct further studies to find out if the signal represents an actual risk.
Further studies are done in safety systems such as the CDC’s Vaccine Safety Datalink (VSD) or the Clinical Immunization Safety Assessment (CISA) project. These systems can better assess health risks and possible connections between adverse events and a vaccine.
VAERS data (without patient information) are publicly available.
The data can be downloaded or searched using CDC WONDER online search tool.
The number of VAERS reports submitted varies each year. In 2019, VAERS received over 48,000 reports. About 85-90% of the reports described mild side effects such as fever, arm soreness, or mild irritability. The remaining reports are classified as serious, which means that the reported adverse event resulted in permanent disability, hospitalization, prolongation of an existing hospitalization, life-threatening illness, congenital deformity/birth defect or death. While these events can happen after vaccination, they are rarely caused by the vaccine.
Adverse event information collected by VAERS includes:
- The type of vaccine received
- The date of vaccination
- When the adverse event began
- Current illnesses and medications
- Medical history
- Past history of adverse events following vaccination
- Demographic information
In some cases, multiple reports are submitted for the same adverse event. For example, the person who experienced the adverse even and their healthcare provider could submit a report for the same adverse event. VAERS scientists review the reports, identify any duplicates, and attach them to the original submission. This review process ensures the same adverse event is not counted more than once, even in cases where there are multiple reports on the same adverse event. Only the primary reports are shown in the public data system, not additional or follow-up reports for the same event.
When evaluating VAERS data, it is important to understand the strengths and limitations.
- VAERS accepts reports from anyone. This also allows VAERS to act as an early warning system to detect rare adverse events.
- VAERS collects information about the vaccine, the person vaccinated, and the adverse event. Scientist obtain follow-up information on serious reports.
- All data (without identifying patient information) are publicly available.
- VAERS is a passive reporting system, meaning that reports about adverse events are not automatically collected. Instead someone who had or is aware of an adverse event following vaccination must file a report.
- VAERS reports are submitted by anyone and sometimes lack details or contain errors.
- VAERS data alone cannot determine if the vaccine caused the reported adverse event.
This specific limitation has caused confusion about the publicly available data, specifically regarding the number of reported deaths. In the past there have been instances where people misinterpreted reports of death following vaccination as death caused by the vaccines; that is a mistake.
VAERS accepts all reports of adverse events following vaccination without judging whether the vaccine caused the adverse health event. Some reports to VAERS might represent true vaccine reactions, and others might be coincidental adverse health events not related to vaccination at all.
Generally, a causal relationship cannot be established using information from VAERS reports alone.
- The number of reports submitted to VAERS may increase in response to media attention and increased public awareness.
It is not possible to use VAERS data to calculate how often an adverse event occurs in a population.
- Vaccine Adverse Event Reporting System (VAERS) - HHSexternal iconThe official website for VAERS. Learn more about this national vaccine safety monitoring system, including what to report, how to report, FAQs, and more.
- For Healthcare Providers: Reporting Adverse EventsSpecific guidance for healthcare providers on which adverse events to report to VAERS and how to report them.
- Video: Vaccine Adverse Event Reporting System (VAERS) Website and Ways to ReportLearn how to report an adverse event using VAERS and how CDC and FDA monitor the safety of vaccines.
- Understanding Side Effects and Adverse EventsLearn more about the difference between side effects and adverse events after vaccination.
- Vaccine Safety ResearchThe latest vaccine safety research and safety studies from CDC.