Data management and quality control
Before starting the study, all units performed training in strict accordance with the requirements of the research program. Epi Data 3.1 software was used to collect the data and conduct consistency check by two clinic doctors. All participating units collected the data in real-time and uploaded the relevant data after the discharge of children, and locked the database after verification. The technical personnel of the team leader kept close contact with all participating units at any time to check case records, verify the accuracy of data, and solve possible problems in time.