Eggs should be safe. Before introducing new chickens, you should quarantine newbies for at least 30 days to prevent any diseases, parasites, virusus being transmitted to your current flock. Thirty days will give you time to visually inspect them, observe and monitor their behavior and make any necessary treatments if there's problems. You should keep them a good distance away from your current flock...some diseases and virusus can be transmitted airborne. Good luck.