I have taken Emgality for 2 months, I just started the 2nd. That's 3 shots the first, and 3 shots the second. My headaches reduced (after a one day spike) from about 5 a day to 2 a day, and now I'm pain free for almost 3 weeks.
As I said in a previous post, there could be some change of season at play here as well, but the reduction in hits was definitely noticeable 24 hours after the first injections.