It's more likely that the reinfections came from different immune responses, where the first infection was beat with a cytotoxic T-cell response (viral defense) but not an antibody response (viral and bacterial defense), the latter of which increases immunity with antibodies.

The re-infection cases that I read about were shown to have been from different strains. Perhaps this is not the common case, but without more information, I am reluctant to accept your statement at face value.

This has not, to my knowledge, happened yet.

> I don't believe any sensible person believes that they become immune to all strains after recovering from one, and I do not believe that Trump was saying this. Do you?

I certainly do believe that the message trump intends to convey is that he is immune to the coronavirus and can no longer be re-infected period.