A puzzling phenomenon: Patients report a rebound of COVID-19 symptoms after taking the antiviral Paxlovid

When it first hit the market in December, the COVID-19 antiviral treatment, Paxlovid, was hailed as a game-changer, an effective medicine that kept at-risk people out of the hospital. But now some patients are reporting on social media an unusual and unnerving phenomenon: their COVID symptoms appear to rebound after taking the medication.

And it’s not just their symptoms that reappear. Many report that after finishing their five-day course of treatment, feeling better, and testing negative on an at-home rapid test, they then test positive again a few days later.

The issue has captured the attention of at least two teams of Boston-area scientists, who are trying to understand what might be fueling the problem. Resistance to the drug? Patients being quickly reinfected? Or maybe some people just need to take the medicine longer to mount a more effective immune response.

Pfizer noted in the documents submitted last fall to federal regulators for its emergency use authorization that “several subjects appeared to have a rebound in SARS-CoV-2 RNA levels around Day 10 or Day 14” but said that “currently there are no clear signals” the virus had developed a resistance to one of Paxlovid’s primary components. The documents said Pfizer would continue analyzing the data.

https://www.bostonglobe.com/2022/04/21/metro/puzzling-phenomenon-patients-report-rebound-covid-19-symptoms-after-taking-antiviral-paxlovid/?event=event12