make it cleaer and fix grammar

Vaccination is introducing a vaccine into the body to produce protection from a specific in the case of Measles it contains antigens.

Vaccination involves introducing a vaccine into the body to provide protection against a specific disease. In the case of Measles, the vaccine contains antigens.

Vaccination involves the introduction of a vaccine into the body with the purpose of providing protection against a specific disease. In the case of Measles, the vaccine contains antigens.