My Cah son is 14.5yrs old. The chicken pox vaccine wasn't available to until after he FINALLY got the pox at the age of 11.5yrs old. He was exposed to them 2 or more times every year since the age of 2, it was begining to look like he would never get them. Luckily he didn't have fever much, but he had pox over his ENTIRE body, he was VERY uncomfortable, we had to double his cortisone until the last poc scabbed over, then gradually wean him back to his regular dose. It was awful for him. Personally, if the shot was available I would have had him get it along with all his other shots. He never had a reaction any worse than a non-CAH child with any of his shots. My non-CAH son, now age 3, recieved the chicken pox vaccine at 1yr old & had no reaction to it at all. I think they only give it to children between the ages of 1yr - 12yrs old. One other experience, I have a cousin who repeatedly gets mild cases of chicken pox...he was told he never got them bad enough to build up an immunity. I think the shot is also supposed to prevent a person from developing shingles later in life, since you only get that if you have had the chicken pox.