Pfizer told by FDA to test additional Paxlovid course in patients with COVID-19 rebound

Pfizer has been told by the US Food and Drug Administration (FDA) to test the effects of an additional course of Paxlovid (nirmatrelvir and ritonavir tablets) among individuals who experience a rebound in COVID-19 after the first course of treatment. The company must produce the initial results of a randomised controlled trial of a second course of the antiviral by 30 September next year, according to a letter from the regulator. The order follows reports of rebounding COVID-19 symptoms after the first course of treatment, which Pfizer said were rare. The FDA said a protocol for the study is expected to be finalised this month.