The vax mandates were Constitutional because the underlying illnesses were lethal to children.
That, my dear, is complete bullshit. You are inventing your own explanations. Are you saying chickenpox is "lethal" to children? Very rarely. I had it; probably you had it. Yet once a vaccine was developed, it was mandated for school kids.
And those lucky children stand no risk of getting shingles today.
As someone else noted, parents can refuse to allow their children to be vaccinated, but they'll have to find some kind of anti-vaxxer school for them.