Vaccination is the administration of antigenic material to stimulate an individual’s immune system to develop adaptive immunity to a pathogen. Vaccines can prevent or ameliorate infectious disease. When a sufficiently large percentage of a population has been vaccinated, herd immunity results

Vaccine Safety

Vaccines are safe and effective. Because vaccines are given to millions of healthy people — including children — to prevent serious diseases, they’re held to very high safety standards. In this section, you’ll learn more about vaccine safety — and get answers to common questions about vaccine side effects.

How are vaccines tested for safety?

Every licensed and recommended vaccine goes through years of safety testing including: Testing and evaluation of the vaccine before it’s licensed by the Food and Drug Administration (FDA) and recommended for use by the Centers for Disease Control and Prevention (CDC)
Monitoring the vaccine’s safety after it is recommended for infants, children, or adults