It stands for Immediate Post Injection Reaction. There's a reaction to Copax that hits about 16% of those on it (per the SS nurse I talked to yesterday, used to be quoted at 1%). Happens within the first few moments of taking the injection, so is literally right after the med is taken.

For me, I first feel like someone just punched me in the gut. Then there's shortness of breath, flushing, tightness in chest, heartbeat increases. Lasts about 10 to 15 minutes. Cool washcloth on back of neck helps a lot. Not laying down makes breathing easier. Having been through it so many times, everyone's surprised at how calm I am when I call. Little do they know it's because I learned the hard way that freaking out makes it ten times worse.

Hope this answered your question a little. My doc advises to take a day off from the shot, so today is a shot free day for me. I'll start up again tomorrow.