I suggest you look into laws surrounding medical neglect of children. The first part of my comment was general, and is specifically describing this very type of parent, but not taken to an extreme. As far as my state laws go
"A parent who denies their child vital and necessary medical treatment faces the following consequences:
• Loss of custody. The child is taken to state custody for protection if the parent is found of negligence.
• Criminal charges. The parent may be charged with child abuse and neglect or even assault if it is proven that he or she has failed in providing the necessary medical attention for the child."
The state take will authority of both situations. I am not sure what the laws are regarding this where you are. HN is a globally accessible website, but discussions are generally US-centric. It wasn't outside the context, I was just not focusing on the very extremes. After you've interacted with this type of parent once or twice, it becomes very easy to identy harmful behavior. I do mean interact with parents that ended up losing custody over neglect. I hope you empathize more with the children stuck in these situations after reading some of the cases. I am not 100% sure what you are attempting to argue.
In my state becoming aware of such behavior and failing to report itself is a crime. I think the crime part only officially applied during when I was associated as an employee of a univeristy and teaching high schoolers. I know I had to do mandated reporter training. The law states every single state resident is a mandated reporter, but I am not sure about the consequences for residents.
The reason vaccination is not covered under this law is because there is it's hard to prove the harm of denying vaccines, in a legal way. There are plenty of people, especially healthcare professionals, that wish vaccination was covered under this kind of law. It is true in some states but not all.
"Results. Our search yielded 9 cases from 5 states. Most courts (7 of 9) considered vaccine refusal to constitute neglect. In the 4 cases decided in jurisdictions that permitted religious exemptions, courts either found that vaccine refusal did not constitute neglect or considered it neglect only in the absence of a sincere religious objection to vaccination.
Conclusions. Some states have a legal precedent for considering parental vaccine refusal as medical neglect, but this is based on a small number of cases. Each state should clarify whether, under its laws, vaccine refusal constitutes medical neglect."
https://www.hg.org/legal-articles/is-denying-medical-treatme...
https://reportingchildabusenj.org/#:~:text=All%20residents%2....
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5308147/