Rare cases of COVID returning pose questions for Pfizer pill

As more doctors prescribe Pfizer’s powerful COVID-19 pill, new questions are emerging about its performance, including why a small number of patients appear to relapse after taking the drug. Paxlovid has become the go-to option against COVID-19 because of its at-home convenience and impressive results in heading off severe disease. The U.S. government has spent more than $10 billion to purchase enough pills to treat 20 million people. But experts say there is still much to be learned about the drug, which was authorized in December for adults at high risk of severe COVID-19 based on a study in which 1,000 adults received the medication.