What we know about COVID-19 and immunity

Since his return from Walter Reed National Military Medical Center, President Donald Trump has repeated that he may now be "immune" to the coronavirus. In a video released shortly after he arrived back at the White House, he said, "Now I’m better, and maybe I’m immune, I don’t know."

In a 55-minute interview on Fox Business, he made several claims about his health and COVID-19 immunity, saying, "When you catch it you get better, and then you’re immune," and jokingly referred to himself as a "perfect physical specimen."

But medical...