Funding for this research was provided by:
National Natural Science Foundation of China (81872637)
Science and Technology Development Program of Pudong Shanghai New District (PKJ2017-Y01])
Shanghai Professional and Technical Services Platform (18DZ2294100)
Shanghai Municipal Commission of Health and Family Planning (201840324)
Received: 22 October 2019
Accepted: 2 September 2020
First Online: 21 September 2020
Ethics approval and consent to participate
: This study was approved by the institute review board of Shanghai Children’s Medical Center. The surveillance protocol was approved by the ethical committee of Shanghai Pudong New Area Center for Disease Control and Prevention. Individual information was anonymized and de-identified prior to analysis. Strict confidentiality of individual data was practiced during the entire study.
: Not applicable.
: The authors declare that they have no competing interests.