I'm an emergency physician on the Navajo Nation in the US. I've seen multiple people quite ill the second time they've caught COVID (based on positive PCR twice

I'm an emergency physician on the Navajo Nation in the US. I've seen multiple people quite ill the second time they've caught COVID (based on positive PCR twice, months apart, with compatible symptoms both times, resolution of symptoms in between, and a negative test in between). All had multiple sick family members the second time, hard to say who infected who, but I have no reason to believe they were not infectious the second time. (All were young and healthy, young children and youngish adults, seems like they were generally not very ill the first time so perhaps didn't mount a very robust immune reaction?) In speaking to colleagues that are hesitant about the vaccine, the evidence that having had COVID once does not guarantee protection against a subsequent and possibly more serious infection is actually something I specifically point out. Note that I'm not arguing that we have evidence that the vaccine guarantees long-lasting immunity either. EDIT: typo