I don't know if there are any papers for Covid in particular but it's how the immune system works in general. AFAIK there is no reason to assume it Covid differ

I don't know if there are any papers for Covid in particular but it's how the immune system works in general. AFAIK there is no reason to assume it Covid differs in that respect. > Those are confirmed cases. That doesn't mean there's only 4 total. I'm sure there are more, but how many? There have been hundreds of millions of infections (according to the WHO). If there are a few dozen or even a thousand reinfections among them, it's not a phenomenon we need to worry about. We could assume that reinfections are common even without any evidence for or against, but then we are playing something akin to Pascal's wager. Also, I think if reinfections were common, by now we would very likely have evidence for that by now.