This is the final story of a five-part series diving into the rise of the anti-vaccine political movement.

For years, groups at the vanguard of the anti-vaccine movement had been operating with relatively small budgets and only a handful of staff.

Now, they're awash in cash.

The Covid-19 pandemic has produced a remarkable financial windfall for anti-vaccine nonprofits. Revenue more than doubled for the Informed Consent Action Network and Robert F. Kennedy Jr.'s Children's Health Defense in 2021 compared to the year prior, according to a POLITICO analysis of tax filings. The nonprofits that survived on operating budgets of around a few million dollars just a few years prior are now raking in more than $10 million each.

"Covid vaccines have been the foot in the door for the more general anti-vaccine movement. And unfortunately, that door is open pretty wide now," said Dr. Dave Gorski, a Michigan-based oncologist who has been tracking anti-vaccine efforts for two decades.