COVID rebound after Pfizer treatment likely due to robust immune response, study finds

A rebound of COVID-19 symptoms in some patients after taking Pfizer's antiviral Paxlovid may be related to a robust immune response rather than a weak one, U.S. government researchers reported on Thursday. They concluded that taking a longer course of the drug - beyond the recommended five days - was not required to reduce the risk of a recurrence of symptoms as some have suggested, based on an intensive investigation of rebound in eight patients at the National Institutes of Health's Clinical Center.