New-onset Severe Headache After Covid-19 Vaccine

Hypotheses: 1. Severe new-onset headache after Covid-19 vaccine occur in a minor subset of vaccinated individuals. 2. Immunological reactivity with activation of trigeminal nociceptors can be among the mechanisms in severe headaches after Covid-19 vaccines. 3. Biomarkers in blood and CSF and imaging findings can be used to assess severe new-onset headache after Covid-19 vaccines. The main aim of the project is to describe the characteristics of severe new-onset headache after Covid vaccine and the treatment effects. Secondary aim: 1. Investigate potential mechanisms and analyse biomarkers to predict treatment effects. 2. To assess at baseline and 6-month follow-up the rate of brain MRI pathology. 3. To assess the change xof brain 18F-FDG PET metabolism from baseline and 6-month follow-up 4. To assess the levels of brain specific biomarkers 5. To assess the level of blood specific biomarkers Duration of Study participation: * Enrollment: 24 months * Follow-up: at 3 and 6 months after inclusion. For those with continued severe headache regular 3-month controls are planned during the study. Total study duration 24 months