If You’ve Had Covid, Do You Need the Vaccine?

When Jonathan Isaac, a prominent basketball player for the Orlando Magic, explained why he chose not to be vaccinated against the coronavirus, he tapped into a dispute that has been simmering for months: Do people who have had Covid-19, as Mr. Isaac said he has, really need the vaccine?

That question has thrust tortuous immunological concepts into a national debate on vaccine mandates, with politicians, athletes, law professors and psychiatrists weighing in on the relative strength of so-called natural immunity versus the protection afforded by vaccines.

But the answer, like nearly everything about the virus, is complicated.

While many people who have recovered from Covid-19 may emerge relatively unscathed from a second encounter with the virus, the strength and durability of their immunity depends on their age, health status and severity of initial infection.

“That’s the thing with natural infection — you can be on the very low end of that or very high end, depending on what kind of disease you developed,” said Akiko Iwasaki, an immunologist at Yale University.