Study Suggests COVID-19 Antiviral Nirmatrelvir Only Benefits Older Adults

Treatment with the oral antiviral nirmatrelvir significantly reduced the rates of hospitalization and death due to COVID-19 during the Omicron surge in patients 65 years of age and older, according to findings from an observational, retrospective cohort study.

To assess the effectiveness of nirmatrelvir, a SARS-CoV-2 main protease inhibitor, in preventing severe COVID-19 outcomes, researchers obtained electronic medical records for members of the Clalit Health Services (CHS), a health care organization covering approximately 52% of the population of Israel. The study period was from January 9, 2022 to March 31, 2022 when the Omicron variant was the dominant strain in Israel.

Researchers identified a total of 109,254 eligible CHS members who were 40 years of age and older, had confirmed SARS-CoV-2 infection, received a COVID-19 diagnosis, and were at high risk for progression to severe disease. There were 3902 patients who received nirmatrelvir therapy. To estimate the association of nirmatrelvir treatment with severe COVID-19 outcomes, a Cox proportional-hazards regression model with time-dependent covariates was used.

Among patients 65 years of age and older, results showed a lower rate of hospitalization due to COVID-19 in nirmatrelvir-treated patients with 14.7 cases per 100,000 person-days compared with 58.9 cases per 100,000 person-days in untreated patients (adjusted hazard ratio [HR], 0.27; 95% CI, 0.15-0.49). The adjusted HR for COVID-19-related death was 0.21 (95% CI, 0.05-0.82). 

Among patients 40 to 64 years of age, no benefit was observed regarding the rate of hospitalization due to COVID-19 in nirmatrelvir-treated patients compared with untreated patients (15.2 cases vs 15.8 cases per 100,000 person-days, respectively; adjusted HR, 0.74; [95% CI, 0.35-1.58]). The adjusted HR for COVID-19-related death was 1.32 (95% CI, 0.16-10.75).

“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 among those who did not,” the study authors concluded. “No evidence of benefit was found in younger adults.”

In December 2021, the Food and Drug Administration issued an Emergency Use Authorization for nirmatrelvir tablets co-packaged with ritonavir tablets (marketed under the brand name Paxlovid) for the treatment of mild to moderate COVID-19 in patients 12 years of age and older weighing at least 40kg with positive results of direct SARS-CoV-2 testing, and who are at high risk for progression to severe COVID-19, including hospitalization or death.

Reference

Arbel R, Wolff Y, Hoshen M, et al. Nirmatrelvir use and severe COVID-19 outcomes during the Omicron surge. N Engl J Med. Published online August 24, 2022. doi:10.1056/NEJMoa2204919