The association between acute transverse myelitis and COVID-19 vaccination in Korea: Self-controlled case series study.

Background: Acute transverse myelitis (ATM) has been reported as a potential association between COVID-19 vaccination. In this study, we aimed to investigate the association between the COVID-19 vaccination and ATM.

Methods: A self-controlled case series study was performed using a large database that combine the COVID-19 vaccine registry and the national claims database. The COVID-19 vaccination data included information on individuals aged 18 and above who received COVID-19 vaccination from February 26, 2021, to August 31, 2022. The claims database covered the entire Korean population for the period between January 1, 2002 to August 31, 2022. Patients who develop ATM within 1-42 days following COVID-19 vaccination were included. The observation period was 270 days after the first dose of the COVID-19 vaccine. The incidence rate ratio (IRR) and 95% confidence interval (CI) were estimated using a conditional Poisson regression model.

Results: A total of 159 ATM patients were included. Among them, 82 (51.6%) were male, and mean age was 55.4 (±17.4) years. The IRR was 2.41 (95% CI: 1.76-3.30) for the ATM risk within 1-42 days after COVID-19 vaccination. The IRR by vaccine product was 3.31 (95% CI: 1.81-6.05) for ChAdOx1-S; 1.99 (95% CI: 1.30-3.03) for BNT162b2; 2.57 (95% CI: 1.14-5.97) for mRNA-1273; and 3.33 (95% CI: 0.30-36.44) for Ad26.COV2.S.

Conclusion: These findings indicated an increased risk of ATM following COVID-19 vaccination within 42 days. An association with the risk of ATM was found both for viral vector and mRNA vaccines.