Important update: Healthcare facilities
CDC has updated select ways to operate healthcare systems effectively in response to COVID-19 vaccination. Learn more
Given new evidence on the B.1.617.2 (Delta) variant, CDC has updated the guidance for fully vaccinated people. CDC recommends universal indoor masking for all teachers, staff, students, and visitors to K-12 schools, regardless of vaccination status. Children should return to full-time in-person learning in the fall with layered prevention strategies in place.
The White House announced that vaccines will be required for international travelers coming into the United States, with an effective date of November 8, 2021. For purposes of entry into the United States, vaccines accepted will include FDA approved or authorized and WHO Emergency Use Listing vaccines. More information is available here.

COVID-19 Vaccine Safety Monitoring Systems

COVID-19 Vaccine Safety Monitoring Systems
Updated Oct. 20, 2023

COVID-19 vaccine recommendations have been updated as of October 3, 2023 to add 2023-2024 updated Novavax COVID-19 vaccine. The content on this page will be updated to align with the new recommendations. Learn more.

What You Need to Know

  • Hundreds of millions of people in the United States have safely received COVID-19 vaccinations.
  • COVID-19 vaccines used in the response to the pandemic underwent the most intensive safety monitoring in U.S. history.
  • Vaccine safety monitoring for the updated COVID-19 vaccines relies on the following systems:
    • Vaccine Adverse Event Reporting System (VAERS)
    • Vaccine Safety Datalink (VSD)
    • Clinical Immunization Safety Assessment (CISA) Project

Vaccine Safety Monitoring Process

After a vaccine is authorized or licensed (approved) for use, multiple vaccine safety systems monitor adverse events following vaccination and look for potential safety problems.

  • CDC vaccine safety monitoring can identify adverse events that may not have been seen in clinical trials. If an unexpected adverse event is seen, experts quickly study it to assess whether it presents a safety concern.
  • Experts then decide whether changes are needed in U.S. vaccine recommendations or clinical guidance.

Vaccine safety monitoring is critical and helps ensure that the benefits of vaccination continue to outweigh the risks.

Vaccine Safety Monitoring Systems

CDC, FDA, and other federal partners use the following systems and data sources to conduct comprehensive vaccine safety monitoring for the following populations:

Existing safety monitoring systems

CDC, FDA, and other federal partners use the following systems and data sources to conduct comprehensive vaccine safety monitoring: