Received: 27 April 2020
Accepted: 20 December 2020
First Online: 13 January 2021
Ethics approval and consent to participate
: The research protocol and informed consent were approved by the ethics committee of Sun Yat-sen Memorial Hospital of Sun Yat-sen University and cooperation agreements were signed with all collaborative members. Consent to participate was obtained from the participants and the parents/guardians of the children under the age of 16.
: Not applicable.
: The authors declare that they have no competing interests.