Unvaccinated stepson

Okay so I’m due 3/31 and it just dawned on me that my stepsons mother “doesn’t believe” in vaccinating. My stepson, according to my husband, has never had any shots. He’s obviously been lucky enough to have remained healthy and not catch any life threatening diseases but now that I’m about to have my own baby, the thought of my stepson being around her is a little unnerving. He is about to turn 11, so we can obviously tell him to be very careful, not touch her face, etc without having to worry if he will understand fully what we’re saying. But it still bothers me.

I brought this up to my husband and he gave me a pretty annoying response. “He’s fine! He doesn’t have mumps or measles or whatever and he is not going to be kept away from his sister” and I totally understand where he’s coming from. Of course he wants his son to meet his baby sister in the hospital. It just kinda makes me a little sick to my stomach that he isn’t more concerned about the fact that his son can potentially expose our newborn baby to disease. I told him to please bring it up to his sons mother but I am 99.9% sure that conversation won’t be effective at all. I think I want to bring it up to my doctor at our next appointment on Tuesday. What do you ladies think? I’m so torn and I dread this whole situation. Help! Lol ☹️