Advice
Working at a company, especially a big one like Pfizer, for just 3 months over the summer really isn't enough time to get your hands into the meat of things. I wasn't fully trained until about 2 months in to what was supposed to be a 6 month co-op, and I think at least part of why they asked me to stay on was because it would be 2 months after they hired a new guy before he would be able to actually fully take over for me. If you can, I would definitely go for a 6 month co-op over a 3 month.