Reported Adverse Events and Associated Factors in Korean Coronavirus Disease 2019 Vaccinations

Despite their effectiveness, coronavirus disease 2019 (COVID-19) vaccines have been associated with adverse effects, underscoring the importance of continuous surveillance to ensure vaccine safety and effective management of public health. Herein, the characteristics and risk factors of vaccine-related adverse events (AEs) were identified to gain an in-depth understanding of vaccine safety by investigating the impact of the vaccination dose on changes in post-vaccination AEs.

Herein, a linked database of COVID-19 vaccination records from the Korea Disease Control and Prevention Agency, AE reports from the COVID-19 Vaccination Management System, and healthcare claims from the National Health Insurance Service, targeting ≥ 5-year-old individuals, was utilized (study duration = February 26, 2021, to January 31, 2023). The frequency and severity of reported post-vaccination AEs were evaluated. Furthermore, we specifically explored AEs in relation to the cumulative dosage of vaccines administered while evaluating associated risk factors.

During the observation period, 42,804,523 individuals completed the COVID-19 vaccination series, with 365,900 reporting AEs, with headache, muscle pain, and fever being the most frequently reported. Notably, the AE reports were approximately twice as high for women than for men, which was further exacerbated following both doses. Analysis by age group revealed that AE reports were lower among children, adolescents, and older adults than in the middle-aged cohort (age = 50-64 years), with higher reports observed for 18-49-year-old individuals. Additionally, a higher risk of reporting was identified among individuals with lower socioeconomic status compared with those of middle socioeconomic status. Excluding dementia, the risk of reporting AEs was high in individuals with underlying diseases compared with those without, for instance, the risk of reporting AEs following two-dose vaccinations was approximately twice as high in individuals with chronic obstructive pulmonary disease and asthma.

These findings indicate that women, younger people, those with a lower socioeconomic status, and those with underlying health conditions reported a higher incidence of AEs following COVID-19 vaccinations. This emphasizes the need for continued monitoring to ensure safe vaccination and address vaccine-related anxiety and fear, especially within the aforementioned groups.