New-onset Severe Headache After Covid-19 Vaccine

Study Design: Prospective observational multi-center study Cohort study of patients with new-onset severe headache after Covid-19 vaccine. Patients referred to the participating headache clinics for severe headache after Covid vaccine will be invited to participate in the study. The invitation will be given in conjunction with their visit to the headache specialist. Patients already diagnosed and treated for severe headache after Covid vaccine will be invited to participate during control visits at the participating centres. After written informed consent information information from the initial phases will be collected retrospectively from the medical records of the patients that have already been diagnosed and started with treatment. Further information will be collected prospectively. For newly diagnosed patients all information will be collected prospectively. Blood samples will be drawn to assess immunological mechanisms. Inclusion criteria: * Patients aged ≥ 18 years with new onset severe headache or severe worsening of pre-existing headache within one week after Covid vaccination and has not resolved within 3 weeks. * Inclusion within 12 months after symptom onset. * Informed written consent signed by the patient. Exclusion criteria: • Patients not available for follow-up assessments (e.g. non-resident).