Treatment with nirmatrelvir was associated with significantly lower rates of hospitalization and death in patients aged 65 years and older infected with the omicron variant of COVID-19. This was among study findings published in The New England Journal of Medicine.
The oral protease inhibitor nirmatrelvir has shown efficacy in treating unvaccinated patients infected with the delta variant of COVID-19, limited data exist on the drug’s effect on those infected with the omicron variant. Researchers therefore sought to assess how well nirmatrelvir prevented severe outcomes of COVID-19 in a population of vaccinated patients during the omicron surge.
The investigators conducted an observational, retrospective cohort study using data obtained from electronic medical records for member of Clalit Health Services (CHS) — a large health care organization that covers approximately 52% of the entire population of Israel and nearly two-thirds of older Israeli adults. The study period commenced on January 9, 2022 — the first day that nirmatrelvir was administered to CHS members — and ended on March 31, 2022. During this study period, the omicron variant was the dominant SARS-CoV-2 strain in Israel. The study included 109,254 individuals 40 years of age and older with confirmed diagnosis of COVID-19 who were at high risk of severe disease. Of those, 3902 (4%) had received nirmatrelvir.
Results of the analysis showed that among participants aged 65 years and older, the rate of hospitalization due to COVID-19 among patients treated with nirmatrelvir was 14.7 cases per 100,000 person-days vs 58.9 cases per 100,000 person-days among those not treated with nirmatrelvir (adjusted hazard ratio [aHR, 0.27; 95% CI, 0.15-0.49). Likelihood of death due to COVID-19 infection was also lower in those treated with nirmatrelvir (aHR, 0.21; 95% CI, 0.05-0.49).
Among patients between 40 and 64 years of age, the rate of hospitalization due to COVID-19 among patients treated with nirmatrelvir was 15.2 cases per 100,000 person-days vs 15.8 cases per 100,000 person-days among those not treated with nirmatrelvir (aHR, 0.74; 95% CI, 0.35-1.58). Among this age group, the analysis did not find a lower likelihood of death from COVID-19 infection in those treated with nirmatrelvir (aHR, 1.32; 95% CI, 0.16-10.75).
Study limitations include the retrospective cohort design, in which various confounders might have caused bias in the observed effectiveness, and the limited number of patients receiving nirmatrelvir.
The investigators concluded that during the omicron variant surge of SARS-CoV-2 infection, “no evidence of benefit [with nirmatrelvir] was found in younger adults.” Future studies are warranted in order to evaluate the short-term and long-term safety of nirmatrelvir therapy in real-world settings.
Disclosure forms provided by the authors are available with the full text of this article at NEJM.org.
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;387(9):790-798. doi:10.1056/NEJMoa2204919