Vaccine Safety

All vaccines used in the United States are required to go through years of extensive safety testing before they are licensed by the US Food and Drug Administration (FDA). FDA and the Centers for Disease Control and Prevention (CDC) work with healthcare providers throughout the US to monitor the safety of vaccines, including for any adverse events, especially rare events not identified in pre-licensure study trials. There are currently three systems used to monitor the safety of vaccines after they are licensed and being used in the US. These systems can monitor side effects already known to be caused by vaccines as well as detect rare side effects that were not identified during a vaccine’s clinical trials.

One of the  three systems used to monitor the safety of vaccines after they are licensed and used in the US is the Vaccine Adverse Event Reporting System (VAERS). VAERS accepts reports from health professionals, vaccine manufacturers, and the general public and receives about 28,000 US reports per year, compared with millions of vaccine doses given to adults.


CDC Clinical Immunization Safety Assessment (CISA) Project

National network of vaccine safety experts from the CDC’s Immunization Safety Office (ISO), seven medical research centers, and other partners, which provides a comprehensive vaccine safety public health service to the nation.

Ensuring the Safety of Vaccines in the United States

Information from the CDC

If You Choose Not to Vaccinate Your Child, Understand the Risks and Responsibilities

If you choose to delay some vaccines or reject some vaccines entirely, there can be risks. Follow these steps from the CDC to protect your child, your family, and others.

Influenza Vaccine Safety

Childhood Influenza Immunization Coaltion (CIIC) FAQs

The Childhood Immunization Schedule and Safety: Stakeholder Concerns, Scientific Evidence, and Future Studies

Institute of Medicine (IOM)

The Journey of Your Child's Vaccine

The vaccines your child gets have a long journey before they arrive at your pediatrician’s office. All along the way, scientists, public health experts, and government officials work to ensure their safety and effectiveness. Learn more about vaccine development, testing, and safety monitoring in pictures and words through CDC’s infographic

Understanding MMR Vaccine Safety

Centers for Disease Control and Prevention (CDC): Frequently asked questions

Understanding the Vaccine Adverse Event Reporting System (VAERS)

Information from the CDC

Understanding Thimerosal, Mercury, and Vaccine Safety

Questions and Answers from the CDC

Understanding Vaccines resource guide on the safety and efficacy of vaccines

Vaccine Confidence Project

London School of Hygiene and Tropical Medicine

Vaccine Information Statements

Vaccine Information Statements (VISs) are information sheets produced by the Centers for Disease Control and Prevention (CDC). They are given to all vaccine recipients and explain both the benefits and risks of a vaccine.