I found out that the vet office is open Saturday mornings, so I gave them a call. The Dr. asked if he was drinking and acting normally, which he is, so she said it was probably a reaction to the vaccines. She recommended not feeding him until this evening, and then just a little bit, and slowly working him back up to his normal feeding schedule. And to call the vet on call if he keeps puking into tomorrow. I feel better! I'll keep you updated. Thanks for the help, everyone!