Received: 12 November 2019
Accepted: 5 March 2020
First Online: 18 March 2020
Ethics approval and consent to participate
: The study protocol was reviewed and granted ethics approval by the Institutional Review Board of the National Institute of Hygiene and Epidemiology (code: 726/QDVSDTTU).
: Not applicable.
: The authors declare that they have no competing interests.