Effectiveness and Duration of Protection of a Fourth Dose of Coronavirus Disease 2019 Messenger RNA Vaccine Among Long-term Care Residents in Ontario, Canada.

Grewal, Ramandip; Nguyen, Lena; Buchan, Sarah A; Wilson, Sarah E; Costa, Andrew P; Kwong, Jeffrey C · J Infect Dis · 2023

retrospective_cohort · Level III

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Abstract

We estimated the effectiveness of a fourth dose of messenger RNA coronavirus disease 2019 vaccine against Omicron infections and severe outcomes over time among long-term care residents in Ontario, Canada. Fourth doses provide additional protection against Omicron-related outcomes, but the protection wanes over time, with more waning seen against infection than severe outcomes.

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