Received: 27 April 2020
Accepted: 9 October 2020
First Online: 14 October 2020
Ethics approval and consent to participate
: All aspects of the study were approved by the Ethics Review Board of the National Institute for Nutrition and Health, Chinese Center for Disease Control and Prevention (2016–015), and written informed consent was obtained from caregivers before the interview.
: Not applicable.
: The authors declare that they have no competing interests.