This is a very common approach and is called an attenuated vaccine[0]. The oral Polio vaccine is such an agent. But it only works if the virus can't out-evolve

This is a very common approach and is called an attenuated vaccine[0]. The oral Polio vaccine is such an agent. But it only works if the virus can't out-evolve the vaccine, the immunity is long-lasting, and if the risk of spontaneous mutations becoming virulent again is low. [0]: https://en.wikipedia.org/wiki/Attenuated_vaccine https://en.wikipedia.org/wiki/Attenuated_vaccine