Unvaccinated stepchild

I am 30 years old. I recently discovered my stepchild has zero vaccines. I have no children, but I would like to have children in the near future. I have concerns about my stepchild being around my babies before they are fully immunized. There was never any custody battle between my husband and the mother of his child. My husband is very worried about “rocking the boat” and causing any issues that would start a battle. We get him 50/50 every other week. I have a wonderful relationship with my 7 yr old stepchild. I also would love to have children of my own. What would you do?