Funding for this research was provided by:
Clinical Research Start Plan project, Southern Medical University (No. LC2017PY001)
Text and Data Mining valid from 2019-07-16
Received: 25 July 2018
Accepted: 3 July 2019
First Online: 16 July 2019
Ethics approval and consent to participate
: The study was approved by the Ethical Committee of the Guangzhou Center for Disease Control and Prevention and the Southern Medical University Research Ethics Committee (GZ-REN-0001). Permission to conduct the study was granted by the Departments of Education and Health. Before the examinations, informed written consent to examine the children was obtained from all parents/legal guardians.
: Not applicable.
: The authors declare that they have no competing interests.