How the Federal Government Monitors Vaccine Safety
Vaccines are essential tools for public health that help prevent millions of hospitalizations and deaths each year in the U.S. alone. Vaccines are also overwhelmingly safe, with serious negative side effects from vaccinations being very rare. Even so, side effects and adverse events do happen, which makes it important to continually monitor vaccine safety and to investigate and respond to serious events that are detected, and to assess whether they are linked to vaccination. For this reason, the federal government has multiple systems in place that track vaccine safety.
Current Federal Vaccine Safety Monitoring Systems
These systems include reviews of data collected during the regulatory review process both before and after vaccines are approved for use, analysis of self-reported vaccine injuries from the public, and ongoing surveillance and analysis of data from patient records at a national level. The following table provides an overview of the main federal systems and databases:
| System Name | Responsible Agency |
|---|---|
| Safety Data from Clinical Trials | FDA |
| Post-licensure Rapid Immunization Safety Monitoring (PRISM) / Biologics Effectiveness and Safety (BEST) | FDA |
| Vaccine Adverse Events Reporting System (VAERS) | FDA and CDC |
| Vaccine Injury Compensation Data | HRSA |
| Vaccine Safety Datalink (VSD) | CDC |
| V-Safe | CDC |
| Clinical Immunization Safety Assessment (CISA) | CDC |
Historical Regulatory Background
Safety monitoring of vaccine products has been subject to federal regulatory oversight for over a century. Federal regulation of vaccine safety began formally with the passage of the “Biologics Control Act of 1902”, which authorized federal review of pharmaceutical products in development and which was created in response to a number of deaths caused by the unregulated use of a diphtheria anti-toxin vaccine in 1901. Subsequent laws expanded and clarified the federal role in protecting the public’s health and regulating the safety of drugs and vaccines, spurred on in some cases by safety events.
For example, the Federal Food, Drug, and Cosmetic Act passed in 1938 following a number of deaths caused by sulfanilamide expanded federal regulatory oversight of the manufacturing, testing, promotion, and distribution of pharmaceuticals. In 1944, the Public Health Service Act (PHSA) was enacted to consolidate and affirm the roles of federal agencies in protecting the public’s health, including review and regulation of pharmaceutical products, and has served as a foundation for continued federal public health efforts. For many decades, vaccines were regulated primarily by the National Institutes of Health (NIH), but in 1972 Congress moved much of the responsibility to the Food and Drug Administration (FDA).
Current Scrutiny and Debates
At the same time, the issue of vaccine safety in the U.S. has been increasingly contested, and is currently facing growing scrutiny, including from Trump administration officials. For example, Department of Health and Human Services (HHS) Secretary Robert F. Kennedy, Jr. has raised questions about vaccine safety, saying he believes the federal government is not doing enough to monitor adverse events and has not been transparent about the data on vaccine safety that it does have. Prior to becoming HHS Secretary, Kennedy said that the federal government had failed to conduct comprehensive studies on vaccine safety and said he believes the federal vaccine safety system captures only a tiny fraction of adverse events from vaccinations.
As Secretary, Kennedy has also said he wishes to overhaul the federal government’s approach to vaccine safety monitoring, including by creating a division at the Centers for Disease Control and Prevention (CDC) to focus on vaccine-related injuries and implementing an automated system to track such injuries. In addition, members of the Advisory Committee on Immunization Practices (ACIP), a key vaccine advisory committee for the federal government that was newly constituted by Kennedy in June 2025, have echoed some of these same concerns about vaccine safety and have pledged to revisit vaccine safety issues through ACIP.
Experts within and outside the government have disputed claims about the lack of sufficient federal vaccine safety monitoring, saying the federal government does in fact have systems in place that can track the safety of vaccines, and that these systems are collectively able to identify important safety signals or significant adverse events from vaccinations. In most cases, these systems have been in place for decades and have been able to identify past vaccine safety issues.