How do vaccines work?

Vaccines train the immune system to recognize and combat pathogens without causing the disease. They contain weakened, inactivated, or harmless fragments of the microorganism (such as proteins or genetic material). When administered, the body produces antibodies and memory cells specific to that pathogen. If exposed later, the immune system recognizes and attacks it quickly, preventing illness. This process provides immunity on both individual and community levels, reducing disease spread. Modern vaccines may use mRNA or viral vectors to safely deliver instructions for generating immune protection.