Why do vaccines train the immune system?
Short answer
Vaccines show the immune system features of a pathogen in a safe form, so it can make antibodies and memory cells. If the same pathogen appears later, the immune system can respond more quickly, helping lower the risks of infection and severe disease.
What are antigens and antibodies?
An antigen is a clue that helps the immune system recognize something as foreign. When the immune system responds to an antigen in a vaccine, or to information for making one, it produces antibodies. Antibodies are proteins that attach to particular antigens.
What does the immune system remember?
The immune system keeps antibody-making cells and memory cells. If it later recognizes the same pathogen’s antigen, it can respond faster than it did the first time. This can help prevent infection or lower the risk of severe disease.
Why are multiple doses sometimes needed?
Vaccines differ in how many doses are needed to build protection and how long that protection lasts. Multiple or booster doses may strengthen the immune response or help restore protection that has weakened over time.
Do vaccines prevent infection completely?
Vaccines do not guarantee 100% protection, and vaccinated people can still become infected. Protection may also take time to develop after vaccination. Vaccination can nevertheless help protect against disease, including by lowering the risk of severe illness. Effects and schedules vary by vaccine, disease, age, and health status, so individual decisions should follow current public guidance and medical professionals.
Key point
Vaccines show the immune system a pathogen’s features in advance and prepare a faster response through antibodies and memory cells. The goal is not “never becoming infected,” but lowering the risks of infection and severe disease.