A Study With Eptinezumab in Adolescents (12-17 Years) With Chronic Migraine

To find out if eptinezumab is better than placebo (normal saline solution) in lowering the number of days with migraine in young people ages 12 to 17 with chronic migraine.

Inclusion Criteria: * The participant has a diagnosis of migraine (with or without aura) as defined by International Classification of Headache Disorders 3 (ICHD-3) guidelines with history of chronic migraine, of at least 6 months prior to the screening visit. * During the 28-day screening period, the participant must adequately complete the headache eDiary on at least 23 of the 28 days following the screening visit. * During the 28-day screening period, the participant must have ≥15 to ≤26 headache days, of which at least 8 are migraine days as documented in the eDiary. Exclusion Criteria: * The participant has previously been randomised in this study and exposed to eptinezumab. * The participant has been exposed to any monoclonal antibody treatment (including exposure in a study) \