When Elliott had his 2 month vaccines, he ran a fever of 101.7. I thought it was high, and almost called his doc. He eventually slept it off though and the fever broke. A couple weeks later he went to the doc to get checked out and she asked how he did with his vaccines. I told her about his fever, and her comment was, "Oh, that's good that he only ran a low grade fever!"
So I guess it is considered low grade for babies. I think of it this way: 100.4 is the highest a normal temp could be for a baby. So 101.5 would be like ours of 99.7 if 98.6 is normal. Yeah, it is up, but nothing crazy. Of course, if the baby got up to 104 or 105 I don't think that would equal our 102 and the doc should be called. But if it's only a degree above I monitor it and give extra snuggles. I try not to give too much medication. He made it through all vaccines so far without.
Hope he feels better though, keep an eye on it! Maybe he is teething! Have you felt anything on his gums?
* I am not doc though, and I am a first time mom so I am going off of instinct only, not facts that I have researched! Just so everyone knows!