In the US we got a head start on it with climate.

In the US,this went mainstream for the pandemic. It was an existing undercurrent in different communities.

Reactionary people weaponized vaccines with Gardasil - good Christian boys and girls are chaste until marriage, so vaccination is unnecessary. Sinners get gods punishment.

Crazy left-wing people cling to the autism rumors about vaccination.

All of this is magnified by politics and propaganda. Certain religious sects punch above their weight because of political factors - you can usually correlate this with measles outbreaks. Foreign influence operations encourage and stoke this stuff to encourage general unrest as well.

In Poland, I first started hearing it around vaccines and climate discussions couple years before COVID - but that may have been because I was hanging out in various social media groups discussing those topics (and/or just mocking the "science deniers"). The term however seems to have exploded in use since the pandemic. I think it's because it suddenly became relevant to mass audience and journalists started using it.