COVID-19 vaccination-triggered cluster headache episodes with frequent attacks

Background The pathophysiology of cluster headache and how cluster episodes are triggered, are still poorly understood. Recurrent inflammation of the trigeminovascular system has been hypothesized. It was noted that some long-term attack-free cluster headache patients suddenly developed a new cluster episode shortly after COVID-19 vaccination. Methods Cases are described from patients with cluster headache who reported a new cluster episode within days after COVID-19 vaccination. All cases were seen in a tertiary university referral center and a general hospital in the Netherlands between March 2021 and December 2021, when the first COVID-19 vaccinations were carried out in The Netherlands. Clinical characteristics of the previous and new cluster episodes, and time between the onset of a new cluster episode and a previous COVID-19 vaccination were reported. Results We report seven patients with cluster headache, who had been attack-free for a long time, in whom a new cluster episode occurred within a few days after a COVID-19 vaccination. Interpretation COVID-19 vaccinations may trigger new cluster episodes in patients with cluster headache, possibly by activating a pro-inflammatory state of the trigeminocervical complex. COVID-19 vaccinations may also exacerbate other neuroinflammatory conditions.