Funding for this research was provided by:
UNICEF (0860/A0/05/502 Health & Nutrition Grant)
Received: 18 August 2019
Accepted: 13 February 2020
First Online: 18 February 2020
Ethics approval and consent to participate
: This study was conducted according to the guidelines laid down in the Declaration of Helsinki and all procedures involving research study participants were approved by the Ethics Review Board of Peking University (approval number IRB00001052–16034). Written informed consent was obtained from all caregivers before data collection.
: Not applicable.
: The authors declare that they have no competing interests.