Vaccine shedding is when an individual releases, or sheds, the components of a vaccine either inside or outside of their body. This can only happen with a certain type of vaccine called a live-attenuated vaccine. Some examples of live-attenuated vaccines: measles, mumps, and rubella (MMR) vaccine, flu nasal spray vaccine (FluMist). chickenpox vaccine, rotavirus vaccine.

Because live-attenuated vaccines can replicate, the weakened pathogen can be shed. But it’s important to note that shedding doesn’t equate with transmission, in which the weakened pathogen is passed to another person. Should these pathogens be passed to another individual, they’re highly unlikely to cause disease.

In addition to live-attenuated vaccines, there are several other types of vaccines. Unlike live-attenuated vaccines, none of these vaccine types contain live pathogens, so they cannot be shed:

Inactivated vaccines which contain a whole, killed version of a pathogen.

Subunit, recombinant, polysaccharide, or conjugate vaccines in which only small pieces or fragments of a pathogen are present.

The mRNA vaccines which instruct cells on how to make proteins associated with a pathogen in order to generate an immune response.

Viral vector vaccines use a modified virus to deliver instructions on how to make proteins associated with a pathogen in order to produce an immune response.

Toxoid vaccines are made up of an inactivated form of a toxin produced by some bacterial pathogens.

More Info: www.healthline.com