It reduces the risk and therefore overall number of infections. Its a bogus argument you're making. I wear a hellet playing hurling to reduce my chance of getting a hurl or sliotar in the noggin. I may still get one but much less chance.
It’s a bogus argument that people that don’t have covid can’t spread covid? Heard it all now.
That analogy doesn’t work, because it wouldn’t stop you taking a whack to the head, it’d just stop it from giving you a broken skull. It wouldn’t make the object disappear.