I'm no expert in this field, hence my dumb question: lets assume we find such an attenuated strain and "infect" people with it such that they could all build the anti-bodies for it. Couldn't the dangerous strain still mutate itself over time in a way where the anti-bodies for the attenuated strain wouldn't help anymore or is this rather considered unlikley (since the virus then would have to become fundamentally different)? In other words, would we then end up with the possibility of similar mutations as with the seasonal flue where this "vaccine" with an attenuated strain would have to be renewed periodically? In any case, thanks for working on this!