What do vaccines prevent?

Vaccines prevent only the Infectious Diseases that they were made to prevent. For example, a vaccine for one type of flu will prevent that type of flu, but you may still get other types if you are not also vaccinated for them. This is why the seasonal flu vaccine usually contains vaccine for the three most likely types of flu that are expected to circulate at the next flu season.

There are vaccines for the various types of influenza, for other viral diseases like measles, mumps and polio and for a very limited number of bacterial disease such as one common type of bacterial pneumonia.

See the related questions below for more information about how vaccines work.