1. Department of Dermatology; Okayama University Medical School; Shikata-cho 2-5-1 Okayama 700 Japan
2. Department of Pediatrics; Okayama University Medical School; Shikata-cho 2-5-1 Okayama 700 Japan
3. Department of Virus Disease and Vaccine Control; National Institute of Health; Musashimurayama 208 Japan