From the Departments of ∗Community Medicine

†Infectious Diseases

‡Biostatistics, Faculty of Medical Science, University of Fukui

§Department of Health and Welfare, Fukui Prefecture

∥Division of Infection and Clinical Immunology, University of Fukui Hospital, Fukui, Japan.

Correspondence to: Osamu Yamamura, MD, PhD, Department of Community Medicine, Faculty of Medical Science, University of Fukui, 23-3 Matsuokashimoaizuki, Eiheiji-cho, Yoshida-gun, Fukui 910-1104, Japan. E-mail: [email protected].

The authors declare that they have no competing interests. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.