Inclusion criteria
Studies were included for the systematic review if they met the following criteria (a) infants, children, and adolescents who had COVID-19 vaccinated by BioNTech-Pfizer vaccine; (b) children and adolescents who had COVID-19, either confirmed microbiologically or clinically, especially those vaccinated by BioNTech-Pfizer vaccine; (c) information on COVID-19 outcome was reported as either ICU admission (ICU and intermediate care), or hospitalization; (d) at least one side effect after receiving BioNTech-Pfizer vaccine.