2.3 Data extraction
Data extraction and validity assessment by two researchers (FNand XC) independently screened and extracted data according to a predetermined proforma in Microsoft Excel Version 16, including: The data were extracted irrespective of the type of vaccine or number of vaccine doses. Data extraction and validity assessment by two researchers (FN and XC) independently screened and extracted data according to a predetermined proforma in Microsoft Excel Version 16,including: 1) bibliometric information: title, first author, date of publication, and the country conducting the studies; 2)details of intervention: type of the vaccine, number of participants receiving each dose of vaccine;3) demographic information: age, sex, and disease;4) general methodological details: length of follow up;5) outcome information: outcomes of safety and details of adverse events. Any Disagreements during the process were resolved by the third researcher (ZR).