However, it does seem that they shed 'something' - probably spike protein or its fragments. It's not catchable or transmissive in the normal sense. I've also thought it might be giving my immune system a good sneak preview for when I do get infected. However, too many reports of Bel's Palsey and other characteristic covid symptoms in people who have spent quite a bit of time with recent vaccinees. As for length of time - who knows. I've made my husband sleep in another bed each time he gets a jab for a couple of weeks an taken my prophylaxis and otherwise don't worry about it.