"Live attenuated" refers to a type of vaccine that contains a weakened form of a virus or bacterium. This weakened pathogen is still alive but has been modified so it cannot cause disease in healthy individuals. By introducing this attenuated organism into the body, the immune system can recognize and respond to it, building immunity without causing illness. These vaccines are effective because they closely mimic a natural infection, prompting a strong and lasting immune response. Examples of live attenuated vaccines include those for diseases like measles, mumps, and rubella. They are typically administered in a single dose and can provide long-term protection.