Coronavirus disease 2019 vaccines and relevant adverse reactions

In order to overcome the global pandemic of the new pathogen, severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), intensive research has been conducted to understand viral pathogenicity, establish effective treatment strategies, and develop vaccines against coronavirus disease 2019 (COVID-19). To prevent COVID-19, a variety of COVID-19 vaccines have been rapidly developed and are currently being administered worldwide. When developing new vaccines, monitoring for adverse events following immunization (AEFIs) has always been important, and some COVID-19 vaccines are particularly effective as new types of vaccines that have not been used before, thus attracting attention to AEFIs. Vaccine administration is carefully conducted while monitoring for AEFI that are being reported from time to time. AEFIs are largely divided into local reactions, systemic reactions, allergic reactions, and adverse reactions to specific diseases or disease- attributable events. In addition, it is classified according to causes, but it is very difficult to confirm the association with the vaccine. Anaphylaxis, which is a systemic reaction among serious allergic reactions, requires immediate treatment and may require testing to determine the cause. In order to increase the vaccination rate and secure herd immunity, there should be no fear of vaccination due to unidentified side effects. Therefore, monitoring of AEFIs is important and causal relationships must be well established based on reliable epidemiological investigations. Current data show that the benefits of a COVID-19 vaccine far outweigh the risk of AEFIs. Future studies should continue to understand the mechanisms and risk factors of identified adverse reactions.