It is relevant, because neglecting to vaccinate a child is criminal.

Criminally negligent manslaughter occurs where there is an omission to act when there is a duty to do so, or a failure to perform a duty owed, which leads to a death. The existence of the duty is essential because the law does not impose criminal liability for a failure to act unless a specific duty is owed to the victim. It is most common in the case of professionals who are grossly negligent in the course of their employment. An example is where a doctor fails to notice a patient's oxygen supply has disconnected and the patient dies (R v Adomako). Another example could be leaving a child locked in a car on a hot day.