Vaccine Adverse Event Reporting System (VAERS)


Important things to know about VAERS

  • VAERS is an early warning system used to monitor adverse events that occur after vaccination. VAERS is the front-line system of a comprehensive vaccine safety surveillance program in the United States. It is one of many systemspdf icon The CDC and the United States Food and Drug Administration (FDA) use to help ensure vaccines used in the United States, including COVID-19 vaccinesare closely monitored for safety.
  • VAERS provides vaccine safety experts with valuable information so they can assess potential vaccine safety issues, including new COVID-19 vaccines. It is particularly useful for detecting unusual or unexpected patterns of health problems (also called “adverse events”) that could indicate a possible safety issue with a vaccine.
  • If a health problem is reported to VAERS, it does not mean that the vaccine caused the problem. It alerts vaccine safety experts to potential issues they may need to assess and warns them to take further action, if necessary.
  • Hundreds of millions of people in the United States have received at least one dose of the COVID-19 vaccine. The majority of reports to VAERS after COVID-19 vaccination have been non-serious adverse events. The CDC provides timely updates on some adverse events reported after COVID-19 vaccination.

How reports enter VAERS

VAERS collects reports of possible adverse events that occur after vaccination. Anyone can submit a report to VAERSexternal iconincluding patients, parents or caregivers, healthcare providers and vaccine manufacturers.

Under Emergency Use Authorization, the FDA requires healthcare professionals to report certain adverse events to VAERSexternal icon that occur after vaccination against COVID-19. The CDC also encourages reporting of any medically significant adverse events, even if it’s unclear if the vaccine caused the health issue. This helps public health officials monitor and track potential safety issues. Learn more about selected adverse events reported to VAERS.

How VAERS reports are reviewed

Vaccine safety experts review all serious adverse event reports submitted to VAERS. A serious adverse event after vaccination is something that causes

  • A permanent disability
  • Hospitalization or prolonged stay in hospital (if vaccinated during hospitalization)
  • Life-threatening disease
  • Birth defects (birth defects)
  • Death

When VAERS staff members follow up on a serious adverse event report, they request the patient’s medical records related to the event to learn more about what happened.

VAERS reports are publicly available, but to protect privacy and confidentiality, they do not contain personally identifiable information.

VAERS limits

VAERS reports alone generally cannot be used to determine whether a vaccine caused or contributed to an adverse event or disease. Some reports may contain incomplete, inaccurate, incidental or unverifiable information. VAERS reports often lack contextual information, such as the total number of vaccinations given or information on unvaccinated groups for comparison purposes. Most reporting to VAERS is voluntary, which means it can be subject to bias. Data from VAERS reports should always be interpreted with these limitations in mind.

Learn more about how VAERS helps monitor vaccine safety.


VAERS and vaccine safety: how does it work?

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