Here are some of the possibilities: 1-They are all positive because of a common source, likely a highly infectious individual. These people all got a bit of the virus, and the virus was able to replicate just enough to be picked up by PCR tests that are very sensitive and can pick up even very small amounts. They are testing people three times a day with PCR tests! They’ll pick up anything and everything, even the tiniest viral amount. The virus was obviously stopped in its tracks, so almost everyone is without symptoms. That sounds like a great outcome to me. A case of vaccine breakthrough is not the same thing as an unvaccinated or non-immune person catching COVID-19. Personally, if I had tested positive while unvaccinated, I’d be worried until it played out. Post-vaccination? For me, testing positive would be but a curiosity unworthy of my anxiety. There’s a reason that vaccine trials and real world data show so few severe cases, let alone hospitalizations or deaths. Post-vaccination, the virus would no no longer be able to surprise my immune system as a novel pathogen, and I’m not that worried whether it replicates just a bit in my nose before getting shut down. The virus in the Yankees case might even have been a variant with some antibody evading features which gives the virus a bit more time to replicate (the mutations act like a disguise that slow down but don’t eliminate its eventual recognition) before the rest of the immune system shuts it down. None of the variants we have are in “disguises” (antibody evading mutations) that are 100% effective in hiding from the totality of the immune system, and it’s quite likely they never will get there.