Treatment of Covid-19 with nirmatrelvir + ritonavir reduces risk of Covid-related hospitalization and deaths among high-risk patients aged 65 years or older, suggests a recent study reported in the New England Journal of Medicine.¹

Data for hospitalization and mortality for at-risk patients, average age 60 years, with confirmed Covid-19 were examined from January 9 to March 31, 2022 when the Omicron variant of concern was the predominant SARS-CoV-2 strain. Out of the 109,254 patients screened, 3902 (4%) were given nirmatrelvir during the study period. The study aimed to examine the effectiveness of nirmatrelvir in preventing adverse outcomes. The data for the study was sourced from Clalit Health Services, a major health service organization in Israel. The first dose of the drug was administered on January 9, 2022. Approximately 80% of the patients had experienced a previous infection or had been vaccinated.

Among 42,821 patients, aged ≥65 years, treated with nirmatrelvir, the hospitalization rate was 14.7 cases per 100,000 person-days (11 treated patients) compared to almost 60 cases per 100,000 person-days (766 untreated patients) among those who did not receive the drug with adjusted hazard ratio of 0.27.

The hospitalization rate among 66,433 nirmatrelvir-treated patients aged 40-64 years was 15.2 cases per 100,000 person-days (7 treated patients) vs 15.8 cases per 100,000 person-days (327 untreated patients) among patients who were not treated with nirmatrelvir (aHR 0.74) showing no statistical between-group difference hospitalization rate.

In the ≥65 year-age group, two patients out of the 2484 treated patients died due to Covid-19, whereas among the 40,337 untreated patients, there were 158 deaths. The aHR for Covid-related mortality was 0.21. In the 40–64-year age group, there was one death among the 1418 treated patients, while 16 patients out of the 65,015 untreated patients died. The aHR for Covid-related mortality was 1.32.

This study conducted during the omicron surge has demonstrated significant beneficial effect of nirmatrelvir treatment in reducing the risk of hospitalization and covid-related mortality among older adults (aged ≥65 years) during the omicron-driven wave, while no such effect was observed in the younger patients aged 40-64 years. This effect was evident regardless of previous immunity.

Nirmatrelvir in combination with ritonavir (available as Paxlovid) was issued EUA as the first oral antiviral for treatment of Covid-19 in December 2021 for the treatment of mild to moderate Covid-19 in adults and children older than 12 years, including patients at high risk of severe disease.

Reference

1. Ronen Arbel, et al. Nirmatrelvir use and severe Covid-19 outcomes during the Omicron surge. N Engl J Med. 2022 Aug 24. doi: 10.1056/NEJMoa2204919.