Published on in Vol 3, No 2 (2020): Jul-Dec
Preprints (earlier versions) of this paper are
available at
https://preprints.jmir.org/preprint/24827, first published
.

1 Longhua District Center for Disease Control and Prevention , Shenzhen , CN
2 Department of Early Childhood Education, The Education University of Hong Kong , Hong Kong , CN
3 JC School of Public Health and Primary Care, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong , CN