New research has scientists more hopeful that lingering antibodies will help COVID-19 patients—even those who had only mild cases—fight off future coronavirus infections. The studies show that months after recovering, patients have antibodies in their blood still able to defeat the virus, the New York Times reports. "The antibodies decline, but they settle in what looks like a stable nadir," said an immunologist who worked on one of the studies, which has not yet been peer reviewed. "The response looks perfectly durable." Another immunologist and author on a study under review now sees reason to be encouraged, though of course more research on all aspects is needed. "This is exactly what you would hope for," he said. "All the pieces are there to have a totally protective immune response."
Scientists can't be sure of immunity until patients successfully fight the virus off after a later exposure. But then, there's also no proof that anyone is contracting the virus more than once. One explanation could be that immune systems are learning from their first exposure to the virus, the way they do with other viruses. Antibodies usually vanish from the blood within months; they can't replenish themselves. "Frankly, that’s not that surprising, because you're not sick anymore," one professor said. But that finding in COVID-19 patients might have sparked an overreaction—concern that immunity, even from a vaccine, might not last long. There are experts less worried about that, per Scientific American. Antibodies are just part of immunity protection anyway, they say in citing reassuring evidence. "The data on the decline of the antibodies is not scary," another viral immunologist said. (Read more antibodies stories.)