Vaccine

A vaccine is a chemical preparation that are usually made up of microorganisms, viruses, or fragments of either. In all the cases the purpose of a vaccine is designed to introduce an antigen into an immune system and teaches the system to fight a virus or pathogen. Once exposed to the vaccine the immune system then begins to create antibodies that can then combat the virus. Then if a person really contracts a virus, then their immune systems will be prepared to combat it.

When in 2254 the USS Enterprise was infected by a Ngultor virus, Dr. Phillip Boyce and Mr. Spock were able to vaccinate the infected systems using an antibody. (EV comic: Flesh of My Flesh)

In 2266, Dr. Leonard McCoy was able to vaccine to a disease that originated from a life prolongation project on Juram V. While the disease allowed the children of the planet to live for centuries until they entered puberty, all the adults died within a few days. (TOS episode: "Miri" and novel: The Cry of the Onlies)

By the 24th century, Federation medicine had discovered a form of vaccine for almost all diseases and illnesses that they had encountered. However, not all diseases had a vaccine readily available so research still continued. In 2365, an outbreak of plasma plague in the Rachelis system led the USS Enterprise-D to transport samples of the most deadly diseases in the Alpha Quadrant to Space Station Tango Sierra, in the hopes that the scientists there could perhaps develop a vaccine. (TNG episode: "The Child")