My nephew came down with an illness the shot was suppose to prevent, the shot caused the illness. Thankfully it was one that could be cleared up with IV antibiotics. Something that happen 1 in hundreds of thousands of shots and documented.   We over vaccinate too soon I think .. too soon. If there are school age siblings then maybe the timing is fine. If it is a baby that stays home and isn't dragged out everywhere then waiting for their system to develop makes sense to me. but to each their own