The fever is pretty normal because his immune system is doing what it should (attacking the dead bacteria/virus, creating antibodies, cataloguing the blueprint for the antibodies, and flushing his system). I know whenever I get a booster and get sick that I REALLY needed that booster (if we already have the antibody stored, then we get no response at all to the vaccine). Because his immune system is working, he's feeling sick, but the *good* news is that (because the it's like a mild cold/flu instead of 3 deadly and 1 highly irritating illnesses which come with HIGH fevers -104+ in addition to the rest of the symptoms : difficulty breathing, swelling, organ damage, etc.)
Tylenol &/or Ibuprofen (for achiness and fever) + a high fat diet (the immune system is almost entirely made of fat with a little protein thrown in for structure) + plenty of rest and some snuggles will take care o' most of the problems)