COVID-19 Vaccination Does Not Increase Risk of idiopathic inflammatory myositis in U.S. Veterans: Study
A new study published in the journal of Arthritis Care & Research found no evidence to suggest that COVID-19 vaccination increases the risk of developing idiopathic inflammatory myositis (IIM). The study analyzed Veterans Health Administration (VHA) records, to provide reassurance amid earlier case reports hinting at a potential association between vaccination and new-onset IIM.
The case-control study focused on Veterans diagnosed with IIM for the first time, identifying 89 patients who met strict criteria. These included having at least 2 IIM-related International Classification of Diseases (ICD) codes, a minimum of one year of VHA enrollment prior to their first IIM diagnosis, and chart reviews confirming the incident nature of the condition. Each of these cases (445) was carefully matched to 5 control patients who shared similar characteristics, including age, gender, race, clinic specialty visits, and year of visit, but had no IIM diagnosis.
This research examined the timing of COVID-19 vaccinations relative to the onset of IIM. They looked specifically at whether patients had received their first COVID-19 vaccine within 30 or 90 days before the “index date,” the date of IIM diagnosis or equivalent for controls. Among the 89 IIM cases, 7 individuals (7.9%) had received the vaccine within 30 days of diagnosis, when compared to 29 controls (6.5%). Statistical analysis yielded an odds ratio (OR) of 1.22, and after adjusting for potential confounders, the adjusted OR was 1.12.
When the timeframe was expanded to 90 days before the index date, 11 case patients (12.4%) and 68 controls (15.3%) had been vaccinated. Here, the odds ratios were slightly below 1 (OR 0.78; adjusted OR 0.74), again showing no statistically meaningful difference. Multiple other time-interval analyses also failed to reveal any significant link between COVID-19 vaccination and new-onset IIM.
These results are important because they are the first to systematically compare the risk of developing myositis after COVID-19 vaccination to a carefully matched control population. The findings do not support a causal relationship between vaccination and incident IIM, providing reassurance to patients and clinicians alike.
Overall, this study adds to the growing body of evidence that COVID-19 vaccines are safe with respect to rare autoimmune muscle disorders. Veterans and the general population can continue to be confident in the benefits of vaccination, without undue worry about triggering IIM.
Reference:
Hernández, C., Schlesinger, N., Rojas, J., Walsh, J. A., Braaten, T. J., Kunkel, G. A., Jones, M., Sauer, B. C., Facelli, J., Cannon, G. W., & Lebiedz-Odrobina, D. (2025). COVID ‐19 Vaccination is not Associated with the Development of Idiopathic Inflammatory Myositis in U.S. Veterans. Arthritis Care & Research, acr.70023. https://doi.org/10.1002/acr.70023
