Recently, Dylan Scott at Vox attempted to explain how anti-vaccinationism arose (boldface mine):

Well, for starters, even though anti-vaccine activism has existed for decades, the movement received a boost with the COVID-19 pandemic and the way it polarized people’s opinions about public health experts. It edged further into the mainstream with Kennedy’s presidential campaign promising to “Make America Healthy Again” — a movement that has found an uneasy home within the Trump administration. After Trump’s election, he nominated Kennedy to be US health secretary and, once confirmed, Kennedy quickly started rolling back the federal government’s support for vaccines.

That sentence is doing a lot of work, in that it ignores what actually happened. We have good evidence that it was a manufactured anti-COVID vaxx campaign, promulgated in no small part by Tucker Carlson (who wanted to boost his ratings). In April 2021, Fox News, led by Tucker Carlson, started Just Asking Questions about the COVID vaccine, and yes, there was a significant decrease in vaccine uptake during Carlson’s anti-vaccine campaign. Meanwhile, professional anti-vaxxers like current HHS Secretary Kennedy piled on to Fox News’ coverage.

This wasn’t ‘polarization’ per se, it was an intentional propaganda campaign, one that was so obviously harmful, even some people at Fox News were bothered by it. ‘Polarization’ on vaccination isn’t like the earth’s magnetosphere, it’s the result of specific choices by specific people and institutions. And those players need to be named.