Funding for this research was provided by:
National Natural Science Foundation of China (81372955)
Qingdao Outstanding Health Professional Development Fund
Qingdao Key Health Discipline Development Fund
the projects of medical and health technology development program in Shandong province (2016WS0309)
BiosTime Maternal and Infant Nutrition and Health Research Fund (2017FYH008)
Received: 10 September 2020
Accepted: 4 February 2021
First Online: 17 February 2021
Ethics approval and consent to participate
: This study was approved by the Ethics Committee and Institutional Review Board of Qingdao Centers for Disease Control and Prevention. Written informed consent was obtained from all participants’s legal guardians. The authors declare that all procedures contributing to this work comply with the ethical standards of the relevant national and institutional committees on human experimentation and with the Helsinki Declaration of 1975, as revised in 2008.
: Not applicable.
: The authors declare that they have no competing interests.