Effectiveness of nirmatrelvir-ritonavir against the development of post-covid-19 conditions among U.S. veterans: a target trial emulation

Abstract: Background: COVID-19 has been linked to the development of many post-COVID-19 conditions (PCCs) after acute infection. Limited information is available on the effectiveness of oral antivirals used to treat acute COVID-19 in preventing the development of PCCs. Objective: To measure the effectiveness of outpatient treatment of COVID-19 with nirmatrelvir-ritonavir in preventing PCCs. DESIGN: Retrospective target trial emulation study comparing matched cohorts receiving nirmatrelvir-ritonavir versus no treatment. Setting: Veterans Health Administration (VHA). Participants: Nonhospitalized veterans in VHA care who were at risk for severe COVID-19 and tested positive for SARS-CoV-2 during January through July 2022. Intervention: Nirmatrelvir-ritonavir treatment for acute COVID-19. Measurements: Cumulative incidence of 31 potential PCCs at 31 to 180 days after treatment or a matched index date, including cardiac, pulmonary, renal, thromboembolic, gastrointestinal, neurologic, mental health, musculoskeletal, endocrine, and general conditions and symptoms. Results: Eighty-six percent of the Participants were male, with a median age of 66 years, and 17.5% were unvaccinated. Baseline characteristics were well balanced between Participants treated with nirmatrelvir-ritonavir and matched untreated comparators. No differences were observed between Participants treated with nirmatrelvir-ritonavir (n = 9593) and their matched untreated comparators in the incidence of most PCCs examined individually or grouped by organ system, except for lower combined risk for venous thromboembolism and pulmonary embolism (subhazard ratio, 0.65 [95% CI, 0.44 to 0.97]; cumulative incidence difference, -0.29 percentage points [CI, -0.52 to -0.05 percentage points]). Limitations: Ascertainment of PCCs using International Classification of Diseases, 10th Revision codes may be inaccurate. Evaluation of many outcomes could have resulted in spurious associations with combined thromboembolic events by chance. Conclusion: Out of 31 potential PCCs, only combined thromboembolic events seemed to be reduced by nirmatrelvir-ritonavir.

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