hi i am 38 and never had chicken pox ??why ,people say i am naturaly immuned what does this realy mean , i come in contact with people and kids all the time who have them or are getting them, i am the school tuckshop lady, last year we had a very bad outbreak in our whole town, people and kids were getting them twice, but not me not even once ,can u please explain to me why or send me some info thank you for your time on this matter