Vaccines are safe and one of the best ways to protect yourself and your family from disease. Vaccines meet the highest standards of safety. The U.S. has the safest, most effective vaccines in history. U.S. law requires that a vaccine go through years of testing in order to get licensed. After licensure, a vaccine continues to be monitored for safety and effectiveness.
Keep reading to learn more about the safety of vaccines.
General Vaccine Safety Information
Parents want to do what's best for their children. They often look to the internet for information to help them make informed decisions for their families. There is a lot of conflicting information about vaccines online, in the media, and in books and magazines. To help parents read accurate and up to date resources, evaluate online health information with these questions.
These vaccine safety sources are trusted:
- Vaccine safety (Centers for Disease Control and Prevention)
- Vaccine Safety Net (World Health Organization)
- Vaccine safety resources (Immunization Action Coalition)
- Common parental concerns (American Academy of Pediatrics)
- Vaccine safety (Vaccinate Your Family)
- Vaccine development, testing, and regulation (History of Vaccines)
- Vaccine safety (Children's Hospital of Philadelphia)
- Vaccines are safe (Vaxopedia)
Monitoring Vaccine Safety
A vaccine goes through many years of regulation, testing, and research before it's licensed. Then the manufacturer must submit an application to the FDA. The FDA reviews all of the research and safety information before it decides to approve or reject the application. When a vaccine is licensed and used, the FDA continues to monitor vaccine safety and effectiveness.
Other national systems in place to monitor vaccine safety include the Vaccine Adverse Event Reporting System (VAERS) and the CDC's Vaccine Safety Datalink project.
The Vaccine Adverse Event Reporting System (VAERS) collects information about possible side effects that occur after administration of a United States-licensed vaccine. VAERS is operated by FDA and CDC. It is a national reporting system that tracks any adverse reactions that anyone may report following immunizations. The system gets reports from healthcare providers, patients, parents, or anyone who witnessed or even just heard of a possible adverse reaction that occurred after getting any vaccine. The public can view VAERS reports. The VAERS website also shares vaccine safety-related information with parents/guardians, health care providers, vaccine manufacturers, state vaccine programs, and others.
There are limits to the system. Importantly, a VAERS report does not mean the vaccine caused the reaction or outcome. It offers a quick way to identify potential vaccine safety concerns. VAERS is set up to help scientists notice trends or reasons they should investigate a possible problem. After possible safety concerns are identified in VAERS, they will be evaluated in other ways that can determine causation, including using systems such as the CDC’s Vaccine Safety Datalink (VSD) and Clinical Immunization Safety Assessment (CISA). Clinical trials data may be revisited or additional studies may be designed to further investigate. By identifying a concern and having multiple groups study it in different ways, concerns identified in VAERS can quickly be further investigated. Find more information or submit a VAERS report here.
CDC partners with eight health care organizations who enter vaccine administration information into a large data system called the Vaccine Safety Datalink. The group then conducts vaccine safety studies based on questions or concerns raised by the data. This project has been going since 1990 and continues today to monitor the safety of vaccines and conduct studies about rare and serious adverse events following immunization. Learn more about the Vaccine Safety Datalink here.
Thimerosal and Washington State Law
A preservative called thimerosal is used in some vaccines to prevent them from becoming contaminated. Thimerosal has trace amounts of ethylmercury (a type of mercury) This prevents vaccines from getting bacteria or fungi in them.
Thimerosal is safe in the amount found in vaccines. The body easily and naturally removes it. However, as a safety measure, a Washington law states that children under 3 years old and pregnant women cannot receive any vaccine containing more than a trace amount of thimerosal. The Washington State Secretary of Health can suspend this law in times of outbreak or vaccine shortage.
Thimerosal in multi-dose vaccines keeps them clean and sterile. It is not harmful to you or your family. Read more about thimerosal and how it is safe for people:
- “Plain Talk About Childhood Immunization (PDF)” (see Chapters 4 and 5)
also available in Spanish (PDF), Russian (PDF), and Ukrainian (PDF). - Thimerosal in Vaccines (Centers for Disease Control and Prevention)