This study looks at how well and safely the medicine Erenumab works to prevent migraines in kids and teens. Migraines are bad headaches that can make you feel sick and sensitive to light or sound. The study is for children aged 6 to 18 who have these headaches sometimes, not all the time. Placebo is a fake medicine used to compare with the real medicine to see which works better.

The study has four parts:

• Screening: Up to 7 weeks to check if you can join.
• Double-blind Treatment Phase (DBTP): 12 or 24 weeks to test Erenumab or placebo.
• Optional Extension Phase: 40 weeks where everyone gets Erenumab.
• Follow-up: 12 weeks to see if you're okay after stopping the medicine.

Key Points:

• This study lasts more than one year, with several visits needed.
• Participants will get injections once a month.
• There may be risks, like side effects from the medicine.

Note: 456 participants are planned to join. You need permission from a parent or guardian to participate.