I think a 15 year old has the capacity to decide for themselves whether they want any medical/treatment or intervention. I think it's an appalling decision. Forced vaccination? Not in anyone's interest.
I haven't vaccinated my younger children because of what happened to my eldest but I already talk about it with my 11 year old (pros & cons) & if he came to me at 15 & said he wanted to be vaccinated I would arrange it for him (even though I do not think it in his best interests) because at 15 he has capacity.
Likewise if he was advised to have medical treatment but didn't want it then at 15 I would listen to him. (And his younger brother when older as well).
A father forcing a child to undergo any procedure when they are old enough to actively decide against is pretty appalling.
I would expect this decision in a younger case but am pretty shocked a 15 year old's opinion wasn't listened to.