Funding for this research was provided by:
National Nature Science Foundation of China (81973140)
Received: 1 April 2020
Accepted: 1 July 2020
First Online: 16 July 2020
Ethics approval and consent to participate
: The study proposal was approved by the Ethics Committee of Southern Medical University, where this study was conducted. Informed consent was not required because Guangzhou Center for Disease Control and Prevention provided the de-identified children mortality data derived from the official death registration system.
: Not applicable.
: The authors declare that they have no competing interests.