[treesprite82]

I'd say anyone who buys into the wave of fearmongering against vaccines is antivax, even if they've had previous vaccinations. Two twins in their 70s choosing not to get vaccinated would fall into this camp.

Conversely, if there's someone for whom medical consensus agrees is legitimately better off without vaccines (e.g: due to some immune system condition), then I wouldn't call them antivax.