Text and Data Mining valid from 2019-12-01
Received: 10 May 2019
Accepted: 14 November 2019
First Online: 5 December 2019
Ethics approval and consent to participate
: All research projects mentioned in the manuscript had undertaken ethics review and received approval from the respective national ethics review committees and the Ethics Review Committee of the World Health Organization, Geneva, Switzerland.
: Not applicable.
: The authors declare no competing interests.