. 2020 Apr 27;8(5):e661–e671. doi: 10.1016/S2214-109X(20)30109-1
© 2020 This is an Open Access article published under the CC BY 3.0 IGO license which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In any use of this article, there should be no suggestion that WHO endorses any specific organisation, products or services. The use of the WHO logo is not permitted. This notice should be preserved along with the article's original URL
This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/).