The following message was posted on one of my blogs, and I thought I would reply online so that everyone could benefit!
Question: MY CHILD WAS GIVEN THE CHICKEN POX VACCINE AND THE DOCTOR AND I DID NOT KNOW SHE HAD THE CHICKPOX THE SAME DAY SHE GOT THE VACCINE. SHE STILL BROKE OUT WITH THE CHICKPOX EVEN THOUGH SHE HAD THE SHOT. MY CONCERN IS WAS THEIR ANY HARM IN GIVING HER THE VACCINE WHEN SHE HAD THE CHICKEN POX?
Answer: There is no need to worry. The chicken pox vaccine is not going to cause any problem to your child. At best it may cause the chicken pox to be milder, at worst it may not make any difference.
In fact we recommend chicken pox vaccine to contacts of an active patient with chicken pox, as it may prevent / reduce the severity of chicken pox in the family member.
I hope this helps!