Recently, a combination drug called Paxlovid™ was made available for the treatment of COVID-19. Paxlovid includes nirmatrelvir, a viral protease inhibitor, and ritonavir, which enhances the effect of nirmatrelvir. In order for SARS-CoV-2 virus to enter cells, the spike protein must be cleaved by a protease. The protease inhibitor prevents that cleavage event from occurring.

Researchers affiliated with Pfizer recently published a study looking at the ability of Paxlovid to prevent hospitalization and death if given early in infection (Hammond J, Leister-Tebbe H, Gardner A, et al. Oral Nirmatrelvir for High-Risk, Nonhospitalized Adults with Covid-19. N Engl J Med. 2022 Apr 14;386(15):1397-1408.). Specifically, these researchers studied non-vaccinated patients who, because of multiple comorbidities, were at high risk of severe COVID-19. Patients were divided into two groups: 1,120 patients received Paxlovid and 1,126 received placebo. All received study treatment within the first three days of symptoms.

The incidence of hospitalization was 0.77% in the treatment group and 7.01% in the placebo group. Whereas no deaths occurred in the treatment group, 7 deaths occurred in the placebo group. The authors concluded, “Treatment of symptomatic Covid-19 with nirmatrelvir plus ritonavir resulted in a risk of progression to severe Covid-19 that was 89% lower than the risk with placebo, without safety concerns.”

It would be of value to also study patients who had been previously vaccinated, naturally infected or both to further determine the impact of this antiviral agent.

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