Real-World Effectiveness of Nirmatrelvir/Ritonavir in Preventing Hospitalization Among Patients With COVID-19 at High Risk for Severe Disease in the United States: A Nationwide Population-Based Cohort Study

Objectives The aim of this analysis was to describe nirmatrelvir/ritonavir real-world effectiveness in preventing hospitalization among high-risk US COVID-19 patients during SARS-CoV-2 Omicron predominance. Design An ongoing population-based cohort study with retrospective and prospective collection of electronic healthcare data in the United States. Methods Data for this analysis were collected from the US Optum® de-identified COVID-19 Electronic Health Record (EHR) dataset during December 22, 2021−June 8, 2022. Key eligibility criteria for inclusion in the database analysis were ≥12-years-old; positive SARS-CoV-2 test, COVID-19 diagnosis, or nirmatrelvir/ritonavir prescription; and high risk of severe COVID-19 based on demographic/clinical characteristics. Potential confounders between groups were balanced using propensity score matching (PSM). Immortal time bias was addressed. Outcome measures Hospitalization rates within 30 (primary analysis) or 15 (sensitivity analysis) days from COVID-19 diagnosis overall and within subgroups were evaluated. Results Before PSM, the nirmatrelvir/ritonavir group (n=2811) was less racially diverse, older, and had higher COVID-19 vaccination rates and a greater number of comorbidities than the non-nirmatrelvir/ritonavir group (n=194,542). Baseline characteristics were well balanced across groups (n=2808 and n=10,849, respectively) after PSM. Incidence of hospitalization (95% CI) within 30 days was 1.21% (0.84%−1.69%) for the nirmatrelvir/ritonavir group and 6.94% (6.03%−7.94%) for the non-nirmatrelvir/ritonavir group, with a hazard ratio (95% CI) of 0.16 (0.11−0.22; 84% relative risk reduction). Incidence within 15 days was 0.78% (0.49%−1.18%) for the nirmatrelvir/ritonavir group and 6.54% (5.65%−7.52%) for the non-nirmatrelvir/ritonavir group; hazard ratio 0.11 (0.07−0.17; 89% relative risk reduction). Nirmatrelvir/ritonavir was effective in African American patients (hazard ratio, 0.35 [0.15−0.83]; 65% relative risk reduction). Relative risk reductions were comparable with overall results across ages and among vaccinated patients. Conclusions Real-world nirmatrelvir/ritonavir effectiveness against hospitalization during the Omicron era supports EPIC-HR efficacy among high-risk patients. Future research should confirm these early real-world results and address limitations.