This study investigates the protection provided by mRNA COVID-19 vaccine booster doses against Omicron-associated severe disease in adults aged 50 and older. The authors use data from Ontario, Canada, and find that booster doses provide strong protection but that it declined during the period of BA.4/BA.5 predominance.
- Ramandip Grewal
- Lena Nguyen
- Jeffrey C. Kwong
