Funding for this research was provided by:
Japan Society for the Promotion of Science (17H02164)
Received: 31 May 2018
Accepted: 10 March 2019
First Online: 18 March 2019
Ethics approval and consent to participate
: The original survey was approved by the Ethics Committees of the WHO and the US Centers for Disease Control (CDC), and by the Ministry of Health, Vietnam. This study was based on analysis of existing public data that are freely available online with all identifier information detached. Permission to access Vietnam dataset was granted thorough GSHS project.
: Not applicable.
: The authors declare that they have no competing interests.
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