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. 2023 Sep 18;77(6):805-815.
doi: 10.1093/cid/ciad287.

Real-World Effectiveness of Nirmatrelvir/Ritonavir on Coronavirus Disease 2019-Associated Hospitalization Prevention: A Population-based Cohort Study in the Province of Quebec, Canada

Jean-Luc Kaboré  1 , Benoît Laffont  1 , Mamadou Diop  1 , Melanie R Tardif  1 , Alexis F Turgeon  2   3 , Jeannot Dumaresq  4   5 , Me-Linh Luong  6 , Michel Cauchon  7 , Hugo Chapdelaine  8   9 , David Claveau  10 , Marc Brosseau  11   12 , Elie Haddad  13 , Mike Benigeri  1
Affiliations

Real-World Effectiveness of Nirmatrelvir/Ritonavir on Coronavirus Disease 2019-Associated Hospitalization Prevention: A Population-based Cohort Study in the Province of Quebec, Canada

Jean-Luc Kaboré et al. Clin Infect Dis. .

Abstract

Background: Nirmatrelvir/ritonavir has shown to reduce COVID-19 hospitalization and death before Omicron, but updated real-world evidence studies are needed. This study aimed to assess whether nirmatrelvir/ritonavir reduces the risk of COVID-19-associated hospitalization among high-risk outpatients.

Methods: A retrospective cohort study of outpatients with SARS-CoV-2 between March 15 and 15 October 2022, using data from the Quebec clinico-administrative databases. Outpatients treated with nirmatrelvir/ritonavir were compared with infected ones not receiving nirmatrelvir/ritonavir using propensity-score matching. Relative risk (RR) of COVID-19-associated hospitalization within 30 days was assessed using a Poisson regression.

Results: A total of 8402 treated outpatients were matched to controls. Regardless of vaccination status, nirmatrelvir/ritonavir treatment was associated with a 69% reduced RR of hospitalization (RR: .31; 95% CI: .28; .36; number needed to treat [NNT] = 13). The effect was more pronounced in outpatients with incomplete primary vaccination (RR: .04; 95% CI: .03; .06; NNT = 8), while no benefit was found in those with a complete primary vaccination (RR: .93; 95% CI: .78; 1.08). Subgroups analysis among high-risk outpatients with a complete primary vaccination showed that nirmatrelvir/ritonavir treatment was associated with a significant decrease in the RR of hospitalization in severely immunocompromised outpatients (RR: .66; 95% CI: .50; .89; NNT = 16) and in high-risk outpatients aged ≥70 years (RR: .50; 95% CI: .34; .74; NNT = 10) when the last dose of the vaccine was received at least 6 months ago.

Conclusions: Nirmatrelvir/ritonavir reduces the risk of COVID-19-associated hospitalization among incompletely vaccinated high-risk outpatients and among some subgroups of completely vaccinated high-risk outpatients.

Keywords: COVID-19; SARS-CoV-2; effectiveness; nirmatrelvir; ritonavir.

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Conflict of interest statement

Potential conflicts of interest. M. R. T. reports an issued or pending patent (US 11,359,010 B2) for humanized anti-S100A9 antibody and uses thereof (no royalties to date). A. F. T. is the chairholder of the Canada Research Chair in Critical Care Neurology and Trauma. M.-L. L. reports consulting fees from Takeda and Merck. H. C. reports grants or contracts from Novartis, Roche, Sanofi, and Merck for participation in COVID-19–related trials (paid to their institution) and unpaid participation on the medical board of an immunodeficient patient advocacy group (Quebec and Canada). M. Brosseau reports a grant from AstraZeneca as the local principal investigator for the Efficacy and Safety of Tozorakimab in Patients Hospitalised for Viral Lung Infection Requiring Supplemental Oxygen (TILIA) study (paid to their institution). E. H. reports an ongoing patent from Immune BioSolutions for an anti–SARS-CoV-2 monoclonal antibody, and an unpaid position as President Elect of the Clinical Immunology Society. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.

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