An attenuated vaccine is one that has been weakened, so that it can’t make you sick, but will still trigger the creation of antibodies and an immune reaction.
Examples of attenuated vaccines include the:
- chicken pox vaccine
- nasal spray flu vaccine
- MMR vaccine
- oral polio vaccine
- oral typhoid vaccine
- rotavirus vaccines
- shingles vaccine
- smallpox vaccine
- yellow fever vaccine
These are all live vaccines and are often described as being “the closest thing to a natural infection.”
The main downside of live, attenuated vaccines, in addition to the fact that they can’t usually be given to people with immune system problems, is that there is always the “remote possibility exists that an attenuated microbe in the vaccine could revert to a virulent form and cause disease.”
That became a concern with the oral polio vaccine and the very small risk of vaccine-associated paralytic poliomyelitis (VAPP). It has not been an issue with other live, attenuated vaccines, such as measles or flu.