Affiliation: | Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea (S.Y. Park, Y.P. Chong, S.-W. Kwon, S.-H. Kim); ;Korea Centers for Disease Control and Prevention, Cheongju, South Korea (W. Choi, S.-W. Park, E.B. Wang, W.-J. Lee, Y. Jee) |