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# Pfizer Required to Conduct Paxlovid Covid Rebound Trial
- URL: https://www.fdaweb.com/pfizer-required-to-conduct-paxlovid-covid-rebound-trial/
- Published: 2022-08-19T12:00:00.000Z
- Updated: 2026-09-14T17:56:34.000Z
- Author: David McFarland
- Tags: Drugs, #legacy-id-D5152552

FDA has revised an emergency use authorization for Pfizer’s Paxlovid (nirmatrelvir co-packaged with ritonavir) for treating mild-to-moderate Covid-19 to require a post-authorization clinical trial in patients with “Covid-19 rebound” and a clinical trial evaluating different durations of treatment in immunocompromised patients with mild-to-moderate Covid-19.

Reports about Covid-19 rebound following a treatment course of Paxlovid have been increasing. Last month, president Biden experienced a Covid rebound after completing his Paxlovid treatment course and testing negative.

According to the [EUA revision](https://www.fda.gov/media/155049/download?ref=fdaweb.com), “Pfizer will conduct a randomized placebo-controlled trial in patients with Covid-19 rebound following an initial treatment course of Paxlovid to evaluate a subsequent five-day treatment course of Paxlovid. Pfizer will provide topline results by September 30, 2023.”