Effectiveness of Molnupiravir Treatment in Patients with COVID-19 in Korea: A Propensity Score Matched Study.

Background: The MOVe-OUT (efficacy and safety of molnupiravir [MK-4482] in non-hospitalized adult participants with COVID-19 [MK-4482-002]) trial reported that the administration of molnupiravir in unvaccinated patients with coronavirus disease 2019 (COVID-19) before the Omicron epidemic showed a preventive effect of 31% against hospitalization and death. However, studies on the preventive effect of molnupiravir against progression to severe disease and death in patients with COVID-19 during the Omicron epidemic are limited. This study aimed to evaluate the preventive effect of molnupiravir against severe/critical illness or death and death in Korean patients with COVID-19 who were vaccinated mostly during the Omicron epidemic.

Materials and methods: This study used large-scale retrospective cohort data to select patients with COVID-19 who were either treated or not treated with molnupiravir, between August 2022 and March 2023, at a ratio of 1 : 4 using the propensity score matching method. In total, 762,768 patients comprised the non- administered group, and 190,692 patients comprised the molnupiravir-administered group. The preventive effect of molnupiravir against severe/critical illness or death and death was analyzed using logistic regression analysis.

Results: The preventive effect of molnupiravir against severe/critical illness or death and death, represented by the odds ratio (OR) and 95% confidence interval (CI), in the molnupiravir-administered and non-administered group was (OR: 0.714; CI: 0.667 - 0.764) and (OR: 0.749; CI: 0.682 - 0.823), respectively. As age increased, the preventive effect against severe/critical illness or death and death increased. The preventive effect against severe/critical illness or death at ≥60 years was (OR: 0.669; CI: 0.624 - 0.717), at ≥70 years was (OR: 0.614; CI: 0.570 - 0.661), and at ≥80 years was (OR: 0.563; CI: 0.515 - 0.615). The preventive effect against death at ≥60 years was (OR: 0.729; CI: 0.663 - 0.802), at ≥70 years was (OR: 0.676; CI: 0.612 - 0.747), and at ≥80 years was (OR: 0.622; CI: 0.554 - 0.698).

Conclusion: Although molnupiravir showed a relatively weak preventive effect against severe/critical illness or death (29%) and death (25%) among patients with COVID-19, it exhibited a stronger protective effect in older patients than in younger patients. In particular, the preventive effect against severe/critical illness or death (44%) and death (38%) in those aged ≥80 years was pronounced. This study strongly suggests that molnupiravir administration can alleviate the burden on the medical system, and treat patients with COVID-19 effectively by reducing its progression to severe disease and death.