Vaccinations work by exposing our body to an infection so that we develop immunity to it. The advantage of a vaccine is that instead of getting the full-blown disease, we can get immunized by taking in a weak version of the infection. So we get immune to a disease without first having to be sick.
Vaccination is recommended throughout life to prevent infectious diseases and their sequelae. Vaccines are crucial to prevent mortality in that 25% of deaths are due to infections. Vaccines are recommended for adults on the basis of a range of factors. Substantial improvement and increases in adult vaccination are needed to reduce the health consequences of vaccine-preventable diseases among adults.