People who think they’ve been exposed to the novel coronavirus are clamoring for antibody tests — blood screens that can detect who has previously been infected and, the hope is, signal who is protected from another case of Covid-19.
But as the tests roll out, some experts are trying to inject a bit of restraint into the excitement that the results of these tests could, for example, clear people to get back to work. Some antibody tests have not been validated, they warn. Even those that have been can still provide false results. And an accurate positive test may be hard to interpret: the virus is so new that researchers cannot say for sure what sort of results will signal immunity or how long that armor will last.