💉 How do vaccines work?
A safe training session for your immune system.
A vaccine is like a training session for your body. It shows your immune system a harmless picture of a germ, so if the real germ ever shows up, your body already knows how to fight it.
Vaccines teach the immune system to recognize a germ without causing the disease. They contain a weakened or inactivated germ, a piece of it (such as a protein), or instructions to make that piece (mRNA vaccines). The body responds by making antibodies and memory cells. If you later meet the real germ, the response is faster and stronger. When enough people are vaccinated, the germ spreads less, which also protects people who cannot be vaccinated: that is herd immunity.
Vaccines elicit adaptive immunity, neutralizing antibodies from B cells and T-cell responses, against defined antigens, and establish immunological memory. Platforms include live-attenuated, inactivated, subunit and conjugate, viral-vector and mRNA vaccines; adjuvants boost innate signaling to strengthen the response. Conjugate vaccines link polysaccharides to carrier proteins to recruit T-cell help, which matters for infants. mRNA vaccines deliver lipid-nanoparticle transcripts that cells translate into antigen before the mRNA degrades. At population level, the herd-immunity threshold is roughly 1 − 1/R₀.
⚡ Quick facts
- Smallpox was declared eradicated in 1980 thanks to vaccination.
- Edward Jenner made the first vaccine in 1796.
- mRNA vaccines do not change your DNA.