A small number of COVID-19 patients are relapsing after taking Pfizer's antiviral pill, raising questions about the drug

Rare cases of COVID returning pose questions for Pfizer pill A small number of COVID-19 patients are relapsing after taking Pfizer's antiviral pill, raising questions about the drug at the center of the U.S. response effort ABC News ABC News

WASHINGTON -- 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.

WHY DO SOME PATIENTS SEEM TO RELAPSE?

Doctors have started reporting rare cases of patients whose symptoms return several days after completing Paxlovid's five-day regimen of pills. That's prompted questions about whether those patients are still contagious and should receive a second course of Paxlovid.

Last week, the Food and Drug Administration weighed in. It advised against a second round because there’s little risk of severe disease or hospitalization among patients who relapse. ...