Gayle Borne has fostered more than 300 children in Springfield, Tennessee. She’s cared for kids who have rarely seen a doctor — kids so neglected that they cannot speak. Such children are now even more vulnerable because of a law Tennessee passed last year that requires the direct consent of birth parents or legal guardians for every routine childhood vaccination. Foster parents, social workers, and other caregivers cannot provide permission.In January, Borne took a foster baby, born extremely premature at just over 2 pounds, to her first doctor’s appointment. The health providers said that without the consent of the child’s...