Effectiveness of Booster mRNA Vaccines Against SARS-CoV-2 Infection in an Elderly Population, South Korea, October 2021–January 2022 . (19th April 2022) - Kim, Jia; Choe, Young June; Jang, Eun Jung; Lim, Do Sang; Kim, Yoo Yeon; Kim, Ryu Kyung; Yi, Seonju; Lee, Sangwon; Park, Young Joon