Covid-19 rebound is probably more common than data suggests, but Paxlovid still effective

 

As the coronavirus evolves, Pfizer's antiviral pill Paxlovid is one of the few treatments that continues to be effective against recent variants.   However, some people who take Paxlovid – including President Joe Biden, first lady Dr. Jill Biden and Dr. Anthony Fauci – experienced a rebound case of Covid-19: a resurgence of symptoms or positive tests just days after completing treatment and testing negative.   “From the data we have so far, Covid-19 rebound is a relatively infrequent event – this is not happening the majority of the time," a CDC spokesperson told CNN. "A small percentage of people with Covid-19 experience a rebound of symptoms, including those who take antiviral medication, such as Paxlovid."   However there’s a wide range of estimates for what that "small percentage" might be – from less than 1% of people who take Paxlovid to more than 10%.   In clinical trial documents submitted to the US Food and Drug Administration last year, Pfizer noted their data shows that about 2% of people showed present or persistent viral load rebound, a share that was similar among both those treated with Paxlovid and the placebo group that wasn't. The data was collected during a time the Delta variant was dominant.   A preprint study that tracked rebound cases during the Omicron wave found that 2-4% of patients experienced a rebound infection or symptoms within a week after treatment, and 5 to 6% had a rebound within a month.   A separate study published in June by researchers from the Mayo Clinic found that about 1% of patients treated with Paxlovid experienced a rebound of symptoms, an average of about nine days after treatment. But according to Aditya Shah, an infectious disease specialist and an author of the report, the true rate is probably closer to 10%.   Despite the potential for a rebound case, experts agree that Paxlovid is still a good treatment option.   The vast majority of people who have a rebound case of Covid-19 after taking Paxlovid have been found to have mild symptoms. Sometimes they may come back stronger, as in Fauci's case, but they remain far from the levels of severe disease that Paxlovid is meant to protect from.