It is true that a vaccination keeps a person from contracting the disease and it keeps the pathogen from finding a susceptible host. Diseases need hosts to infect in order to survive. A vaccination is good because it keeps the disease from finding another host and therefore limits the spread of the disease. A vaccination also hinders the mutation process that is possible when a disease can adapt over time to be resistant to certain vaccinations. So limiting the hosts and limiting the spread of the disease keeps individuals healthy and diseases from adapting and spreading.
