How Do Vaccines Work?

Vaccines work by training your immune system to recognize and fight specific diseases without causing the illness itself. When you receive a vaccine, it contains weakened or inactive parts of a pathogen (or instructions to make them), which trigger an immune response. Your body produces antibodies and memory cells that 'remember' this pathogen. If you're later exposed to the real disease, your immune system can respond quickly and effectively, often preventing illness entirely or significantly reducing its severity. This is called acquired immunity. Vaccines have eliminated smallpox globally and reduced cases of polio by 99%. Different types of vaccines work in slightly different ways: some use dead viruses, others use weakened live viruses, and newer mRNA vaccines provide instructions for your cells to make a harmless piece of the virus that triggers immunity.