Which type of vaccine can replicate in the body?

Live attenuated vaccines are designed to contain a weakened form of the virus or bacteria that causes the disease. Because these microorganisms are live but attenuated (meaning they have been modified to reduce their virulence), they are capable of replicating in the body. This replication stimulates a strong and prolonged immune response, as the immune system recognizes the live organism as a threat and mounts a defense against it. This leads to the formation of memory cells that can provide long-lasting immunity should the body encounter the actual pathogen in the future.

In contrast, inactivated vaccines are made from pathogens that have been killed, meaning they cannot replicate in the body. Subunit vaccines consist of only parts of the pathogen, such as proteins or sugars, and therefore also do not replicate. DNA vaccines work by introducing a piece of genetic material from the pathogen to elicit an immune response, but these do not replicate in the same way that live attenuated vaccines do.

Thus, the key characteristic of live attenuated vaccines is their ability to replicate, which is essential for generating robust and lasting immunity.