No absolute rules. There are no absolute rules for this. Remember that your newborn just came from a very protected environment (the womb) so when you do start to take your baby out, keep contact and stimulation to a minimum, as they gradually learn to handle the changes in their environment. For the first couple of weeks, have family and friends come to see you and the baby, rather than going out to see them.
Define out. You can take your child out of the house at virtually any age. You should avoid obviously sick people with your newborn, but do not feel like you cannot bring your child out. Current recommendations do recommend that anyone who has contact with a newborn be vaccinated against whooping cough or pertussis.