Funding for this research was provided by:
Bill and Melinda Gates Foundation (OPP50838)
Received: 27 February 2021
Accepted: 14 April 2021
First Online: 17 May 2021
: About the survey component, the study protocol was approved by the Institutional Review Boards of the Institute of Social and Medical Studies (ISMS, Hanoi, Vietnam) and of FHI 360 (NC, USA). Written informed consent was obtained from all participants.
: Not applicable.
: The authors declare no conflict of interest.