This corner of the Bay Area had become a prime example of a highly educated, affluent community with low childhood vaccination rates, driven by a contingent of liberal parents skeptical of traditional medicine. Marin was something of a paradox to mainstream Democrats, and often a punching bag. In 2015, during a measles outbreak in California, the comedian Jon Stewart blamed Marin parents for being guilty of a “mindful stupidity.”

But Marin is the anti-vaccine capital no more.

In the pandemic age, getting a Covid-19 shot has become the defining “vax” or “anti-vax” litmus test, and on that account, Marin County has embraced vaccines at rates that surpass the vast majority of communities in the nation. It comes after public health efforts to change parents’ opinions, as well as a strict state mandate that students get vaccinated for childhood diseases.

And as the nation has grown more polarized, Marin residents are less comfortable wearing the “anti-vax” label increasingly associated with conservatives. Americans who identify as Democrats are more than twice as likely to be vaccinated and boosted against Covid — and Marin County is one of the bluest enclaves in America.

“It kind of became the cool thing to do to get vaccinated,” said Naveen Kumar, physician-in-chief for Kaiser Permanente San Rafael Medical Center.