All About Vaccines

How Vaccines Work

Vaccines work by training your immune system to recognize and fight off harmful viruses or bacteria before they can cause serious illness. Here’s how it works:

Introduction of an Antigen
A vaccine contains a harmless form of a virus or bacteria (or a piece of it), called an antigen. This can be an inactivated or weakened (live attenuated) virus (e.g., MMR, flu vaccine), a protein or part of the pathogen (e.g., HPV, Tdap), mRNA instructions to make a harmless piece of the virus (e.g., COVID-19 mRNA vaccines)

Immune System Response
Once introduced, your immune system detects the antigen as **foreign** and starts building a defense by:
Producing **antibodies** that neutralize the virus or bacteria
Activating **T cells**, which help destroy infected cells and remember the invader

Immune Memory Formation
After the vaccine, your immune system "remembers" the pathogen. If you’re exposed to the real virus later, your body **responds quickly**, preventing illness or reducing its severity.

Long-Term Protection
Some vaccines provide **lifelong immunity** (e.g., measles), while others require **boosters** (e.g., tetanus, flu shots) to maintain protection.

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