My son has been vaccinated for chickem pox when he was a baby. He is now 10 years old and has these ant bite looking bumps on his bottom. the started on the left side of his buttock last night and have seemed to spread to his right buttocka and down the back of his legs. He currently has not been lethargic or running any fevers he says he feels fine. I asked him if the bumps itched and he said only when he touches them, and when he does itch them he says they hurt. Can this be normal signed for chicken pox in a child that has been vaccinated? I am concerned because they have spread, but not too concerned because other than the bumps he has no symptoms. what should I look for??