I don't think it's easy to summarize in a useful manner because it basically comes down to how a specific vaccine works. For example, subunit vaccines like the

I don't think it's easy to summarize in a useful manner because it basically comes down to how a specific vaccine works. For example, subunit vaccines like the whooping cough vaccine use a portion/fragment of the infectious agent, which means it is literally impossible for such a vaccine to cause the illness it is supposed to work on since there is none of that agent in the vaccine in the first place. Attenuated vaccines, such as some polio vaccines and the MMR vaccine, include a weakened version of the infectious agent. These types of vaccines can result in a full-blown infection, especially in immunocompromised people. So in short, the risk of a full-blown infection from a vaccine is going to depend on the type of vaccine, and I suspect there's variation within each type as well. There's more info on the various types of vaccines at https://www.hhs.gov/immunization/basics/types/index.html https://www.hhs.gov/immunization/basics/types/index.html