How Vaccines Work

How Vaccines Work

Vaccines teach a person’s immune system to recognize and respond to a specific bacteria or virus. A vaccine introduces antigens from a bacteria or virus – substances that can prompt an immune response – into the body. Once introduced, the immune system learns how to recognize them and produce antibodies – proteins that recognize and bind to antigens and keep the body healthy. If a person is exposed to the bacteria or virus in the future, their immune system is trained and ready to protect them from infection and disease.   

Vaccines protect our communities and those who cannot be vaccinated. When enough individuals are vaccinated (the herd), the spread of disease from person to person decreases and disease transmission is stopped. When most people are immune to a disease, this is called herd immunity. This protects individuals who are too young, immunocompromised, or otherwise unable to receive a vaccine.

Vaccine Safety

Vaccines are safe and effective in preventing disease and death. Vaccines undergo rigorous testing and surveillance. Safety testing begins as soon as a new vaccine is developed, continues until it is licensed (or otherwise authorized for use), and is monitored indefinitely. The AAP knows and trusts that the vaccines routinely offered to children are safe, effective, and save lives.