Adverse Events Occurred within 30 Minutes Following COVID-19 Vaccination at Bang Sue Central Vaccination Center, Bangkok, Thailand, July to December 2021

COVID-19, with a case fatality rate of 0.98%, requires treatment based on severity of illness. Vaccination is crucial for preventing virus spread and decreasing severity of illness, yet it may lead to side effects. This study explored the 30-minute adverse events following immunization (AEFI) after receiving COVID-19 vaccination at Bang Sue Central Vaccination Center (BSCVC). Data (demographic profile of vaccines, type of vaccines administered for the first and second doses and occurrence of AEFI within 30 minutes) from 871,446 vaccine administrations from July to December 2021 at BSCVC were analyzed. There were 386 occurrences (44.29 per 100,000 doses of vaccine administered) of 30-minute AEFI, with females experiencing AEFI twice as often as males. The highest AEFI rate was with the ChAdOx1 nCoV-19 vaccine (62.68 cases per 100,000 vaccinations). First doses resulted in nearly four times more AEFI than second doses. When considering the second dose, the heterologous regimens had more AEFI than the homologous regimens. Common AEFI symptoms included dizziness/lightheadedness (34%), palpitations/chest tightness (16%), and numbness (11%). No serious AEFI was observed. Further monitoring of AEFI across all vaccination centers in the country should be done including causality assessments for any serious AEFI reported.