1 Department of Pediatrics, Tokyo Medical University, Tokyo, Japan; Division of Infectious Diseases and Immunology, Saitama Children's Medical Center, Saitama, Japan. Electronic address: sato.satoshi.am@pref.saitama.lg.jp.
2 Department of Pediatrics, Tokyo Medical University, Tokyo, Japan.
3 Department of Gastroenterology and Hepatology, Tokyo Medical University, Tokyo, Japan.
4 Division of Infectious Diseases and Immunology, Saitama Children's Medical Center, Saitama, Japan.