I wish I had one! I read up on it pretty obsessively at the time... but that was more than ten years and two computers ago now and I don't still have the citations. I do remember reading about it specifically in the context of breastfeeding and digestive illnesses in infants, and deciding on that basis to delay it with all the other vaccines, and then when we got to the one year mark and went in for the first immunizations, our pediatrician was like "oh, he doesn't need that one because it's only dangerous for babies."