title: Reply.
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors.forename: Eun-Jeong
authors.initials: EJ
authors.lastname: Joo
authors.affiliation: Department of Occupational and Environmental Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, South Korea.|Center for Cohort Studies, Total Healthcare Center, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, South Korea.|Department of Clinical Research Design & Evaluation, SAIHST, Sungkyunkwan University, Seoul, South Korea.
authors.forename: Yoosoo
authors.initials: Y
authors.lastname: Chang
authors.affiliation: Department of Occupational and Environmental Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, South Korea.|Center for Cohort Studies, Total Healthcare Center, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, South Korea.|Department of Clinical Research Design & Evaluation, SAIHST, Sungkyunkwan University, Seoul, South Korea.
authors.forename: Seungho
authors.initials: S
authors.lastname: Ryu