Final answer:
Live attenuated vaccines are vaccines that expose an individual to a weakened strain of a pathogen to activate the immune defenses. An example is the measles, mumps, and rubella (MMR) vaccine.
Step-by-step explanation:
Live attenuated vaccines are vaccines that expose an individual to a weakened strain of a pathogen in order to establish a subclinical infection and activate the adaptive immune defenses. These vaccines stimulate a more comprehensive immune response and can even lead to natural transmission of the attenuated pathogen to other individuals. An example of a live attenuated vaccine is the measles, mumps, and rubella (MMR) vaccine.