Our son will be 4 Nov 1st :)  He has salt wasting CAH and is up to date with all of his immunizations..   Usually before I take him in I give him a dose of Tylenol as a  preventitive to any fever he may get.  However he has done really well with each of his shots and hasn’t needed to be double or trippled dosed.. I even have him receive the flu shot as a preventative measure, as he has an older brother in school who is in the 2nd grade where sneezing and coughing on one another is second nature.  He has done really well with this also, and hasn’t yet needed to be double dosed for any reaction or fever from the shot.. When he was a baby before I had him receive the flu shot he came down with the flu and we ended up in the emergency room having to hydrate him, took him nearly 2  1/2  iv bags before he was able to start releasing the fluid.. since then I have always made sure to get him the shot every year and he’s done great with it... Good luck with your daughter, and I agree the childhood diseases are far more dangerous to our children than the possibility of fever from an immunization.  Your Endo can tell you if there are any questions on what to do, follow your gut, you know your daughter and can tell if she’s feeling her usual self or if maybe she needs a double dose.