The spectrum of non-fatal immune-related adverse events following COVID-19 vaccination: The population-based cohort study in Seoul, South Korea

Much of the current literature on the adverse effects occurring after the coronavirus disease-2019 (COVID-19) vaccination focused on serious adverse events (AEs). Consequently, the non-serious AEs have yet to be comprehensively elucidated. This study aims to investigate the incidence rate and risk of non-serious AEs including gynecological, hematological, dermatological, ophthalmological, otologic, and dental problems following the COVID-19 vaccination. We conducted a population-based cohort study was conducted with the National Health Insurance Service (NHIS) database in Seoul, South Korea. The cumulative incidence rate (cIR) per 10,000 population, Odds ratio, and Hazard ratio (HR) with a 95% Confidence Interval (CI) were measured to assess the non-serious AEs, as reported by the Vaccine Adverse Event Reporting Center, after COVID-19 vaccination. The cIR of non-serious AEs for three months was significantly higher in vaccinated subjects than in non-vaccinated subjects, except for endometriosis. The vaccination significantly increased the risks of all the non-serious AEs except for visual impairment. The risk of inner ear disease showed the highest HRs (HR [95% CI] = 2.37 [2.15-2.60]) among the non-serious AEs following COVID-19 vaccination. Among the vaccinated subjects, heterologous vaccination was associated with the increased risk of most of the non-serious AEs. The three-month risks of incidental non-serious AEs are substantially higher in the COVID-19 vaccinated subjects than in non-vaccinated controls. Our findings suggested that vaccinated subjects with predisposition are potentially vulnerable to the occurrence of broad-spectrum AEs although the COVID-19 vaccines may not be serious.