Which type of vaccine contains a weakened form of the pathogen?

Live attenuated vaccines contain a weakened form of the pathogen responsible for causing a specific disease. The term "live attenuated" refers to the method by which the pathogen is modified to reduce its virulence while still allowing it to replicate in the host's body. This mimics a natural infection, leading to a robust immune response that includes both antibody and cellular immunity.

By using a weakened form of the pathogen, these vaccines often provide long-lasting immunity with fewer doses compared to other vaccine types. Vaccines that are inactivated do not use live pathogens, while subunit and conjugate vaccines are composed of specific pieces of the pathogen (like proteins or sugars) rather than the whole organism in a weakened state. The unique characteristic of live attenuated vaccines is their ability to stimulate a strong immune response similar to natural infection, making them an effective choice for certain diseases.