“It is an obligation to listen to the doctors (Maharik Shoresh 159, Shevut Yaakov 1:65, Yalkut Yosef Kitzor Shulchan Aruch Laws of the Doctor and the Obligation to be Cured 2).”
This has been accepted halachah for a thousand years.
Not vaccinating your children also violates the prohibition of following in the ways of the sectarians: The State of California found that the school that had the largest fraction by far of unvaccinated children was the one run by the Berg Kabbalah Centre cult.