To date, little is known about the evidence of a potential risk of psychiatric adverse events following COVID-19 vaccination in large populations with adequate study design.

To investigate whether COVID-19 vaccination is associated with increased risk of psychiatric adverse events.

We used South Korea’s linkage database to obtain registry data and claims data from 2019 to 2021, and conducted a population-based self-controlled case series study including 11 751 806 individuals. Primary outcomes included anxiety/nervousness, mood disorders, perceptual disturbances/psychoses, aggression/behavioural disturbances, cognitive impairments and sleep disorders within 21 days of COVID-19 vaccination. Secondary outcomes were the stratified primary outcomes according to each individual’s psychiatric history. Conditional Poisson regression was used to estimate incidence rate ratios (IRR) and 95% confidence intervals.

COVID-19 vaccination did not increase the rate of anxiety and nervousness (adjusted IRR 0.95, 95% CI 0.95–0.96), mood disorders (adjusted IRR 0.75, 95% CI 0.75–0.76), perceptual disturbances and psychoses (adjusted IRR 0.72, 95% CI 0.70–0.74), aggression and behavioural disturbances (adjusted IRR 0.93, 95% CI 0.89–0.97), cognitive impairment (adjusted IRR 0.68, 95% CI 0.67–0.69) or sleep disorders (adjusted IRR 0.90, 95% CI 0.89–0.91). Secondary outcomes were consistent with the primary outcome, although the adjusted IRRs for anxiety and nervousness (adjusted IRR 1.17, 95% CI 1.15–1.18) and sleep disorders (adjusted IRR 1.07, 95% CI 1.06–1.09) were statistically significant in individuals with no history of psychiatric disorders. Sensitivity analyses showed consistent results with our main findings.

Our findings provide short-term safety profiles for COVID-19 vaccines regarding psychiatric adverse events. Continuous monitoring of anxiety/nervousness or sleep disorders after COVID-19 vaccination is required regardless of history of psychiatric comorbidities.