How do vaccines work?

Vaccines work by training the immune system to recognize and fight specific pathogens (such as viruses or bacteria) without causing the disease itself. Here’s how vaccines typically work:

1. Introduction of Antigen: A vaccine contains a harmless part of a pathogen, known as an antigen, which could be a dead or weakened form of the pathogen, a piece of the pathogen (like a protein), or a blueprint for making that piece (such as messenger RNA in some vaccines). This antigen stimulates the immune system.

2. Immune Response Activation: When the vaccine is administered (usually by injection), the immune system recognizes the antigen as foreign and activates an immune response. This includes the production of antibodies (proteins that can specifically bind to the pathogen) and the activation of T-cells (cells that help destroy infected cells or assist other immune cells).

3. Memory Formation: After the immune response is triggered, the body generates memory cells (memory B-cells and memory T-cells). These cells “remember” the specific antigen and remain in the body long after the vaccination.

4. Protection Upon Exposure: If the person is later exposed to the actual pathogen (e.g., a virus or bacterium), their immune system recognizes it quickly because of the memory cells. The immune system can then mount a rapid and effective response, producing antibodies to neutralize the pathogen and activate immune cells to destroy infected cells, thus preventing illness or reducing the severity of the disease.

In summary, vaccines prime the immune system by exposing it to an antigen without causing illness, helping the body “learn” how to defend itself if it encounters the real pathogen in the future.