✓ Accepted Answer
Vaccines work by training your immune system to recognise a specific pathogen without causing the actual disease. The immune system has a remarkable memory — once it encounters and defeats a pathogen, specialised memory cells remain that enable a much faster, stronger response to future encounters.
Traditional vaccines do this by exposing you to a weakened or killed version of the pathogen, or to a harmless protein from its surface. mRNA vaccines (like COVID-19 vaccines) take a different approach: they deliver genetic instructions that cause your own cells to temporarily produce the target protein, triggering the immune response.
Herd immunity — when enough of a population is immune that the pathogen can no longer spread easily — protects vulnerable people who cannot be vaccinated. The threshold varies by how contagious a disease is. For measles, about 95% immunity is needed. For COVID, lower because it's less contagious.
Vaccines are among the most impactful medical interventions in history. Smallpox is eradicated. Polio is nearly gone. Measles, diphtheria, and tetanus once killed millions annually.
by makenanjoroge67134