One a baby has had hfmd is he immune to it or can they get it again?

Yes, it's a viral contagious disease that unfortunately can strike again if the child comes in contact with an infected child. My daughter caught it twice in the period of 3 months, and it was such a crazy period for us. She was 5 years old then, so she was able to tell us where it hurts/itches and she kept saying that she doesn't want to eat cause it hurts. The 2nd time round when she caught it again, she simply had no mood to do anything and cried because she thought that there was something "wrong" with her and she couldn't go to school. Her kindergarten was closed for about 2 weeks because there were other kids who were infected with HFMD as well.