My son had a pretty severe reaction to MMR when he was 12 months old. He broke out in hives all over his body and we had to take him to the ER where he was admitted overnight. Luckily, that's the only reaction we have had with his shots. However, we have not followed the guidelines for vaccines that are out by the CDC and have opted for a delayed schedule. He only has one shot at a time and at least one month in between shots. He will not get his 2nd shot of MMR due to the severe reaction the first time around. I've been told by multiple pediatricians that if they have a severe reaction the first time, the 2nd will be worse.
My son is heading into K in the fall and is currently on schedule with his vaccinations w/ the exception of MMR.
I think a delayed schedule is the way to go and not to get so many done especially in the first year.