My daughter had the vaccine at age 1.  When she was 3, she was exposed to chicken pox at school and actually contracted it!  She had very few pock marks, but had a fever as high as 104!  She was on triple dose for 6 days, as well as the alternating doses of Tylenol and Motrin.  We had to give her alot of fluids, including Pedialyte, to be safe, and bathe her when the fever was high.  She made it through without incident.  I don't know if it would have been alot worse without the vaccine.  At least she did not have the severe itching.  Some children need injections with a fever.  If this is the case with your child, you will have to be extra careful (call endo and follow instructions).  Hope this helps.