A study of more than 180,000 COVID-19 survivors found that those vaccinated prior to infection had a lower risk of developing fibromyalgia compared with unvaccinated patients.
Investigators analyzed electronic health records from a large international database, comparing outcomes between 90,508 vaccinated and 90,508 unvaccinated patients. Within 1 year, 242 vaccinated individuals developed new-onset fibromyalgia vs 289 in the unvaccinated group.
“The [adjusted] hazard ratio (HR) for [fibromyalgia] in the vaccinated group was 0.843 (95% confidence interval [CI] = 0.710–0.999), indicating a reduced risk compared to the unvaccinated group,” said lead study author Aihui Liu and colleagues. This reflected a 15.7% reduced risk among vaccinated patients.
When fibromyalgia or mortality was considered as a composite outcome, the HR was 0.820 (95% CI = 0.746–0.901), still favoring the vaccinated group.
Fibromyalgia is a chronic condition characterized by widespread musculoskeletal pain, fatigue, and sleep disturbances. It affects an estimated 2% to 4% of the global population. Previous research suggested that COVID-19 infections may trigger fibromyalgia-like symptoms in some individuals, possibly as a result of inflammatory or immune responses.
To minimize confounding, the investigators used propensity score matching to balance both groups by age, sex, race, comorbidities, and prior health care utilization.
Subgroup analyses revealed more pronounced risk reduction in specific populations. Among men, vaccinated individuals had a 48% lower risk of developing fibromyalgia (HR = 0.520, 95% CI = 0.342–0.792). Those with a body mass index (BMI) under 30 had a 43.6% lower risk (HR = 0.564, 95% CI = 0.347–0.918). The protective effect was also observed in individuals with depression (HR = 0.552, 95% CI = 0.365–0.835) and anxiety disorders (HR = 0.598, 95% CI = 0.425–0.841).
The investigators proposed that vaccination may lower fibromyalgia risk by modulating the inflammatory response. Previous studies have shown that vaccinated patients with COVID-19 infections exhibit lower levels of inflammatory markers such as interleukin-7 and tumor necrosis factor–alpha, which are also elevated in fibromyalgia.
Sensitivity analyses supported the main findings across several scenarios, including broader international data sets, different definitions of unvaccinated status, and varying patterns of health care utilization. In patients with severe COVID-19 infections requiring hospitalization or mechanical ventilation, the vaccine wasn't associated with a statistically significant reduction in fibromyalgia risk.
Limitations of the study included reliance on electronic health records, which may not have captured all diagnoses, and a lack of data on individual-level variables such as autoimmune status or genetic predisposition.
Despite these limitations, the findings suggested that COVID-19 vaccination may provide an additional benefit beyond reducing acute illness—potentially lowering the risk of developing fibromyalgia in some populations.
The authors reported no competing interests.
Source: BMC Medicine