Basically, when they found a vaccine for Polio, people fought it because the government made it mandatory in the US. The people in the United States went nuts. A Polio infection is one of the worst diseases around though. Attacks the spinal column and does terrible things to people. They kind of needed to force it upon people, even if they didn't want it.
It's nothing like a flu.
Of course we couldn't get away without people denying the need for a COVID vaccine and trying to compare it (incorrectly) to polio. They're already gearing up for thinking they're going to be forced to be vaccinated like Polio in the US but obviously COVID is one completely different thing. Implying this might be forced on them.