3 year old is lethargic and feverish after chickenpox vaccine- help?

My 3.5 year old is the most energetic child I know, and since Thursday, after her chickenpox vaccine (very past due), she has had a fever between 100 and 103, and is very tired, all the time, and her mood is very "blah"... very low energy. It's saddening me and worrying me a bit, as I am skeptical and uneasy anyway regarding vaccines. Is this normal...? It's Sunday... when should I call a doctor?