Funding for this research was provided by:
the National Science and Technology Major Projects for the Control and Prevention of Major Infectious Diseases in China (2018ZX10305409-001-004, 2017ZX10104001-005-010)
the National Science and Technology Major Projects for the Control and Prevention of Major Infectious Diseases in China (2017ZX10103004-004)
National Science and Technology Supported Projects (2013BAI09B11)
Received: 14 November 2019
Accepted: 15 May 2020
First Online: 30 May 2020
Ethics approval and consent to participate
: The study protocol was approved by the Ethical Review Committee of Beijing Children’s Hospital. Informed consent was obtained from the guardians of all participants, including screened patients, eligible patients, and the ones received our telephone follow-up. As it is a retrospective, non-interventionist study, it was decided as appropriate to request the verbal consent of each of the patients, and the ethics committee approved this procedure.
: Not applicable.
: The authors declare that they have no competing interests.