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.
