Can harmless viruses be engineered to deliver vaccine payloads for different, actually harmful viruses?
Can harmless viruses be engineered to deliver vaccine payloads for different, actually harmful viruses?
It would be nice to just be automatically vaccinated for everything just by hanging out.
Yes. There are virus vector vaccines already in existence: https://en.wikipedia.org/wiki/Viral_vector_vaccine
For example, adenovirus vector vaccines were created for COVID-19: https://en.wikipedia.org/wiki/COVID-19_vaccine#Adenovirus_vector_vaccines
Those are non-replicating though.
Live attenuated vaccines also exist -- which can replicate -- but those work by using a weakened/modified version of the original harmful live virus the vaccine is intended to protect against: https://en.wikipedia.org/wiki/Attenuated_vaccine
Oral polio vaccine is a well-known example.