Baby vomiting... help.

My 2 month old threw up really bad this morning. He had his shots on Monday. He threw up while getting the oral rotovirus vaccine so I don't think he actually absorbed any of it. He's seemed fine since the vaccines just sleeping more. This morning he didn't eat as much and then threw up quite a lot. He seems fine, he's acting totally normal. Hasn't eaten again cause this just happened. No fever. I'm wondering at what point should I see a doctor for possibility of dehydration !?!  Please note that just calling the doctor is not an option where I live- You have to go see them.