Funding for this research was provided by:
Japan Agency for Medical Research and Development
Ministry of Eucation, Culture, Sport, Science & Technology
Received: 21 February 2018
Accepted: 1 March 2019
First Online: 11 March 2019
Ethics approval and consent to participate
: The research protocol was approved by the Nagasaki University Ethical Review Board, the National Institute of Hygiene and Epidemiology scientific review committee in Hanoi, and the Khanh Hoa Provincial Health Service ethical review board. Written informed consent was obtained from the parents or guardians prior to sample collection and the interviews.
: Not applicable.
: The authors have no conflicts of interest to declare. The corresponding author LMY is an associate editor of BMC infectious Diseases Journal.
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