The implications of Covid-19 reinfection reports are complicated

There have now been at least four cases of Covid-19 reinfection, but the most recent one — in a man in Nevada — is what's giving experts pause. Contrary to experts' expectations, a 25-year-old Reno man was more seriously ill with his second infection, needing hospitalization. But there are still unanswered questions about this case. Experts thought second infections would be milder because the immune system would recognize a familiar foe to put up enough of a fight to prevent serious illness. So, what happened with the Nevada case? Also unknown is if those reinfected are contagious, or how common reinfection is. The world has now seen 25 million Covid-19 cases, so as one expert tells STAT's Andrew Joseph, the focus ought to be: “What happens to most people?” Read more in an explainer here.