Active vaccines are a type of immunization that use a live, weakened version of the pathogen to stimulate a person's immune system to create antibodies to fight the pathogen. There are two types of active vaccines: live attenuated vaccines and recombinant vaccines.
Live attenuated vaccines are made by weakening a naturally occurring virus or bacteria so that it can no longer cause disease, but still provoke an immune response. This type of vaccine is designed to replicate in the body so that it can stimulate a long-term immunity to the pathogen. Examples of live attenuated vaccines include the measles, mumps, rubella (MMR), chickenpox, and yellow fever vaccines.
Recombinant vaccines, on the other hand, are made by taking pieces of genetic material from the virus or bacteria and inserting them into a harmless virus or bacteria. This type of vaccine does not replicate, but instead stimulates the immune system to recognize and fight the pathogen when encountered in the future. Examples of recombinant vaccines include the hepatitis B, human papillomavirus (HPV), and rotavirus vaccines.
Both types of active vaccines can provide protection against the target pathogen, although the protection may not be lifelong. Booster shots may be required for both types of vaccines to maintain protection.