He discuses that in his blog. There are 2 types of such vaccines. Live ones, that are exactly like you said, low infectious strain, and dead ones, where they k

He discuses that in his blog. There are 2 types of such vaccines. Live ones, that are exactly like you said, low infectious strain, and dead ones, where they kill the virus and it sometimes still produces correct antibodies. there are several of such types of vaccines in development