The anti-viral drug nirmatrelvir (Paxlovid™), which is a protease inhibitor, has been shown to significantly decrease hospitalization and death if given to those suffering from COVID-19 during the first few days of infection. The initial study, which showed about 90% efficacy in preventing serious illness, was performed on those who were not immune, either from previous infection or vaccination (Hammond J, Leister-Tebbe H, Gardner A, et al. Oral nirmatrelvir for high-risk, non-hospitalized adults with Covid-19. N Eng J Med. 2022, Apr 14;386(15):1397-1408.) To determine whether nirmatrelvir is also effective in those who are immune to the virus, researchers in Tel Aviv, in collaboration with researchers at Harvard University School of Medicine, studied the effects of the anti-viral agent on patients who were more than 40 years of age (Arbel R, Wolff Sagy Y, Hoshen M, et al. Nirmatrelvir use and severe Covid-19 outcomes during the Omicron surge. N Engl J Med. 2022, Sep 1; 387(9): 790-798).

About 3,900 patients received nirmatrelvir during the study period. Researchers found that for those 65 years of age and older, the rate of hospitalizations due to COVID-19 was 14.7 cases per 100,000 person-days among treated patients compared with 58.9 cases per 100,000 person-days among untreated patients. Among patients 40-64 years of age, the rate of hospitalization due to COVID-19 was 15.2 per 100,000 person-days among treated patients and 15.8 cases per 100,000 person-days among untreated patients.

The authors concluded, “Among patients 65 years of age or older, the rates of hospitalization and death due to Covid-19 were significantly lower among those who received nirmatrelvir than in those who did not. No evidence of benefit was found in younger adults” (p. 790).

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