Data extraction
We extracted as many relevant variables as possible from the information provided (age, date, etc.) and according to the main stratification variable, author, country, data source, age range, study timeframe, baseline population group, outcome (symptoms after vaccination, severity symptoms), total sample, others. We additionally included another category of the length of stay in the hospital or ICU. We retrieved data on the age who are confirmed vaccinated by BioNTech-Pfizer COVID-19, confirmed symptoms after vaccination, and length of stay in hospitals or ICU from publicly available data. All studies included in this review were published in the United States of America (USA).