Background We examined the effectiveness of molnupiravir and nirmatrelvir/ritonavir in reducing hospitalization and deaths in a real-world cohort of non-hospitalized COVID-19 patients. Methods This was a territory-wide retrospective cohort study in Hong Kong. Non-hospitalized COVID-19 patients who attended designated outpatient clinics between 16 February and 31 March 2022 were identified. Patients hospitalized on the day of the first clinic appointment or used both oral antivirals were excluded. The primary endpoint was hospitalization. The secondary endpoint was a composite of intensive care unit admission, invasive mechanical ventilation use, and/or death. Results Of 93,883 patients, 83,154 (88.6%), 5,808 (6.2%), and 4,921 (5.2%) were oral antiviral non-users, molnupiravir users, and nirmatrelvir/ritonavir users respectively. Compared to non-users, oral antiviral users were older and had more comorbidities, lower complete vaccination rate, and more hospitalizations in the previous year. Molnupiravir users were older, and had more comorbidities, lower complete vaccination rate, and more hospitalizations in the previous year than nirmatrelvir/ritonavir users. At a median follow-up of 30 days, 1,931 (2.1%) patients were hospitalized and 225 (0.2%) patients developed the secondary endpoint. After propensity score weighting, nirmatrelvir/ritonavir use (weighted hazard ratio 0.79, 95%CI 0.65-0.95, P = 0.011) but not molnupiravir use (weighted hazard ratio 1.17, 95%CI 0.99-1.39, P = 0.062) was associated with a reduced risk of hospitalization than non-users. The use of molnupiravir or nirmatrelvir/ritonavir was not associated with a lower risk of the secondary endpoint as compared to non-users. Conclusion Use of nirmatrelvir/ritonavir but not molnupiravir was associated with a reduced risk of hospitalization in real-world non-hospitalized COVID-19 patients.

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