Abstract: Objective To analyze and compare adverse events (AE) associated with three emergency licensed COVID-19 vaccines (i.e., Pfizer, Moderna, and Janssen) based on data from the Vaccine Adverse Event Reporting System (VAERS). Methods Data on AE associated with Pfizer, Moderna, and Janssen collected from the days the three vaccines were approved until June 30, 2022 was retrieved from VAERS database respectively. The combinatorial biomedical statistical methods were used to identify statistically significant AE. The profiles of AE were classified and represented by the Ontology of Adverse Events (OAE) for further analysis. In addition, statistical analysis based on detailed information in case reports of death was conducted to identify the major variables that might affect the occurrence of death. Results Eighty-one statistically significant AE were identified, including 67 related to Pfizer, 9 related to Moderna, and 11 related to Janssen. These AE mostly involved the cardiovascular system and behavioral and neurological conditions. Statistical analysis of case reports of death showed that the age, gender, and medical history of the vaccinated individuals had some specific effects on the occurrence of death. Conclusion The three COVID-19 vaccines have a wide safety profile with only minor and self-limiting AE. The causal association between COVID-19 vaccines and consequent AE (especially serious AE) deserves more study.

Key words: COVID-19, vaccine, adverse event, vaccine adverse event reporting system, Pfizer, Moderna, Janssen