A retrospective cohort study: is COVID-19 BNT162b2 mRNA vaccination a trigger factor for cluster headache?

Objectıve Cluster headache (CH) is a coronavirus 2019 (COVID-19) vaccination-related adverse event. There are a few case reports of relapses or de novo cluster episodes following the vaccine. The disease's pathophysiology is still not clear. The most widely accepted mechanism is activation of the trigeminocervical complex (TCC). However, the correlation between vaccination and CH is unexplainable. Its goal is to compare the CH bouts of patients before and after the vaccine. Methods Patients with a history of CH and who had never experienced COVID-19 illness during the pandemic were included in this retrospective cohort analysis. The semi-structured survey was administered face to face to 24 CH patients (16 male). The headache features before and after vaccination were detailed in this survey. Results 18 patients got vaccinated twice, and 6 of them had no vaccination. After the first vaccination, 83.3% of them had CH bout; after the second vaccination, 72.2% of them had CH bout. We divided headache episodes into three groups: (1) before vaccination, (2) after the first vaccination, and (3) after the second vaccination. The third group had a higher pain intensity (9.30 ± 0.630, p = 0.047) and remitting longer (20.00 ± 5.40 days, p = 0.019) than the other groups. The management of the 53.3% bouts after vaccinations was less effective than the usual episodes. Conclusion Most ECH patients experienced new bouts more intense and longer duration after vaccinations than their previous bouts, the mechanism, and pathogenesis of the bouts are the subject of future research. The new studies can be a light for understanding the CH pathophysiology more deeply.