Oh Boy! These are difficult cases as a lot of issues arise, Freedom of Religion, parental rights etc. etc. That being said I would fall on the side of state intervention as the child cannot meaningfully take steps to obtain his own medical care and treatment. If prayer worked my daughter would be alive today.(She also had the finest medical care.)
If prayer worked my son would still be alive. I prayed so hard that I was literally crying, pleading in the hospital chapel. It was a Catholic hospital. God sometimes has other plans for our lives.