I wouldn't say that. I think anti-vax is more people actively and vocally trying to stop others from getting vaccines or spreading misinformation about one or multiple types of vaccines.
A person choosing not to participate may or may not be anti-vax. The choice isn't the determining factor imo.
I posted that because i inferred from brandon's post it's all or nothing. He may have meant he thinks rfk is anti vax. Things can get lost in translation with forum posts.