COVID-19 vaccination elicited de novo and recurrence of cluster headache: A case series

Background: Recent pharmacovigilance studies suggested that cluster headache could be a potential adverse effect after coronavirus disease-2019 (COVID-19) vaccination; however, the possibility of coincidence could not be excluded. Detailed case studies might help elucidate their potential link and implicate potential pathogenic mechanisms. Methods: Patients who developed cluster headache in close temporal relationship to COVID-19 vaccination were identified from two tertiary medical centers in Japan and Taiwan respectively through 2021–2022. Detailed characteristics of the headaches and time between the onset of the index cluster episode and antecedent COVID-19 vaccination were reported. In patients with previous cluster headaches, the duration from previous bout was also recorded. Results: Six patients with new cluster headache bout 3–17 days after COVID-19 vaccination were identified. Two of them were de novo cases. The others either had been attack-free for a long time or developed new cluster bout in seasons atypical to prior bouts. The vaccines included mRNA, viral vector, or protein subunit vaccines. Conclusions: COVID-19 vaccines, regardless of vaccine types, may elicit de novo or relapse of cluster headache. Future studies are needed to confirm the potential causality and explore the potential pathogenic mechanism.