Objective: The efficacy of nirmatrelvir–ritonavir for hospitalized patients with COVID-19 has not been fully established.
Methods: We conducted a retrospective analysis of hospitalized COVID– 19 patients with high risk for disease progression at Beijing Chaoyang Hospital from October 15, 2022, to March 31, 2023. Patients ≥ 18 years old who were hospitalized with COVID-19 within 5 days of symptom onset were included. Baseline data were obtained from the routine electronic health record database of the hospital information system. Outcomes were monitored at 28 days via electronic medical record reviews or telephone interviews.
Results: We identified 1120 patients hospitalized with COVID-19 during the study period. After exclusions, 167 nirmatrelvir–ritonavir users and 132 controls were included. 28-day all-cause mortality rate was 12.0% (20/167) in the nirmatrelvir–ritonavir group, versus 22.7% (30/132) in the control group (unadjusted log-rank p = 0.010; HR = 0.49, 95% confidence interval [CI] = 0.28– 0.86, IPTW-adjusted HR = 0.58, 95% CI = 0.40– 0.86). The 28-day disease progression rates did not differ between the two groups (unadjusted HR = 0.59, 95% CI = 0.34– 1.02, IPTW-adjusted HR = 0.73, 95% CI = 0.50– 1.06). Nirmatrelvir–ritonavir significantly reduced all-cause mortality and disease progression within 28 days among patients aged ≥ 65 years without ≥ 2 vaccine doses.
Conclusion: We found significantly reduced all-cause mortality in the nirmatrelvir–ritonavir group, particularly in elderly patients who were incompletely vaccinated. Future randomized controlled studies are needed to validate our findings.

Keywords: nirmatrelvir–ritonavir, COVID-19, hospitalized