If everyone is vaccinated and the disease disappears (and kills few people) anti-vaxxers think: “why do we vaccinate everyone? The disease didn't kill anyone... and it disappeared."
In headache case, the link between illness and cure is instantaneous.
But when it comes to vaccination, due to the time needed for everything to take effect (many people need to be vaccinated, it takes time) anti-vaccines are unable to link the vaccine to a cure for the disease.
For humans, time changes everything, even the ability to make a connection between illness and cure.
If everyone is vaccinated and the disease disappears (and kills few people) anti-vaxxers think: “why do we vaccinate everyone? The disease didn't kill anyone... and it disappeared."