As the number of people infected with the coronavirus surpasses 450,000 worldwide, and more than one billion are locked in their homes, scientists are wrestling with one of the most pressing questions of the pandemic: Do people who survive the infection become immune to the virus?
The answer is a qualified yes, with some significant unknowns. That’s important for several reasons.
People who are confirmed to be immune could venture from their homes and help shore up the work force until a vaccine becomes available, for example. In particular, health care workers who are known to be immune could continue to care for the severely ill.
Growing immunity in the community also is the way the epidemic ends: With fewer and fewer people to infect, the coronavirus will lose its toehold and even the most vulnerable citizens become more insulated from the threat.
Immunity may also bring an early treatment. Antibodies gathered from the bodies of those who have recovered may be used to aid those struggling with the illness caused by the coronavirus, called Covid-19.
On Tuesday, the Food and Drug Administration approved the use of plasma from recovered patients to treat some severe cases. A day earlier, Gov. Andrew M. Cuomo announced that New York would become the first state to begin testing serum from people who have recovered from Covid-19 to treat those who are seriously ill.
“It’s a trial for people who are in serious condition, but the New York State Department of Health has been working on this with some of New York’s best health care agencies, and we think it shows promise,” Mr. Cuomo said.