They need to be forbidden to travel.
An unvaccinated French boy is suspected of reintroducing measles to Costa Rica after the Central American country had been free of the disease for five years. The five-year-old boy, who was on holiday with his parents, had never had a measles jab and the arrival of the highly contagious disease has sparked concern about the anti-vaccine movement. It is not clear why the child was not vaccinated. The World Health Organisation (WHO) warned last month that “vaccine hesitancy” was among the 10 most serious threats to human health.
Anti-vaxxers are a plague. A true plague.