Paxlovid Weaker Against Current COVID-19 Variants

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Sept. 22, 2023 -- A real-world study published in JAMA Open Network found that Pfizer's COVID-19 antiviral Paxlovid is now less effective at preventing hospitalization or death in high-risk patients as compared to earlier studies. But when looking at death alone, the antiviral was still highly effective. 

Paxlovid was about 37% effective at preventing death or hospitalization in high-risk patients compared to no treatment. The study also looked at the antiviral Lagevrio, made by Merck, and found it was about 41% effective. In preventing death alone, Paxlovid was about 84% effective compared to no treatment and Lagevrio was about 77% effective, the study said.

The University of North Carolina Gillings School of Global Public Health and the Cleveland Clinic examined electronic health records of 68,867 patients at hospitals in Cleveland and Florida who were diagnosed with COVID from April 1, 2022, to Feb. 20, 2023.

For Paxlovid, the effectiveness against death and hospitalization was lower than the effectiveness rate of about 86% found in clinical trials in 2021, according to Bloomberg

The difference in effectiveness in the real-world and clinical studies may have occurred because the early studies were conducted with unvaccinated people. Also, the virus has evolved since those first studies, Bloomberg reported. 

Researchers said Paxlovid and Lagevrio are recommended for use because they reduce hospitalization and death among high-risk patients who get COVID, even taking recent Omicron subvariants into account.

"These findings suggest that the use of either nirmatrelvir (Paxlovid) or molnupiravir (Lagevrio) is associated with reductions in mortality and hospitalization in patients infected with Omicron, regardless of age, race and ethnicity, virus strain, vaccination status, previous infection status, or coexisting conditions," the study says. "Both drugs can, therefore, be used to treat non-hospitalized patients who are at high risk of progressing to severe COVID-19."

Both drugs should be taken within 5 days of the onset of COVID symptoms.