But their resistance is woven together by a common thread: the involvement of a law firm closely tied to the anti-vaccine movement.

Attorneys from Siri & Glimstad — a New York firm that has done millions of dollars of legal work for one of the nation's foremost anti-vaccination groups — are co-counsel in a case against the Durham County Sheriff's Office. They've sent warning letters to officials in Rock County, Wis., as well as to the president of Rutgers University and other schools.

The legal salvos show that a groundswell against compulsory immunization is being coordinated, at least in part, from a law office on Park Avenue in midtown Manhattan. And they offer a window into a wide-ranging and well-resourced effort to contest vaccine requirements in workplaces and other settings critical to the country's reopening — a dispute with sweeping implications for public health, state authority and individual rights.