What does the term "attenuated" refer to in the context of vaccines?

The term "attenuated" in the context of vaccines specifically refers to a weakened form of a pathogen, which means that the pathogen has been modified so that it can no longer cause disease in healthy individuals. This is accomplished through various methods, such as growing the pathogen in conditions that weaken it or using genetic engineering to reduce its virulence. Therefore, when an attenuated vaccine is administered, it stimulates the immune system to recognize and mount a response against the pathogen without causing the illness that the full-strength pathogen would.

The use of an attenuated pathogen in vaccines is beneficial because it helps create long-term immunity by mimicking a natural infection. Attenuated vaccines are typically effective with just one or a few doses, as opposed to inactivated vaccines, which might require multiple doses to achieve similar immunity.