As the new coronavirus continues to spread, patients who have recovered from Covid-19 still need to be careful, said doctors, scientists and public-health experts, who warn that no one is sure just how long immunity to the disease lasts.
It’s a question scientists are still working on, and the answer has significant implications for vaccine development and public-health guidelines. For now, physicians are cautioning patients to continue following social-distancing and mask recommendations even after they have recovered from…