Welcome to Pay Dirt—exclusive reporting and research from The Daily Beast’s Lachlan Markay on corruption, campaign finance, and influence-peddling in the nation’s capital. For Beast Inside members only.

Facebook’s advertising platform is being used to widely circulate anti-vaccine conspiracy theories and misinformation as the nation is attempting to control the resurgence of childhood illnesses that can easily be prevented through vaccinations.

PAY DIRT compiled data on seven Facebook pages now running promoted anti-vaccine posts in the United States. Together, they have bought 147 ads on the platform, ads that have been viewed between 1.6 million and 5.2 million times. They overwhelmingly target women over the age of 25—about 72 percent of the people who viewed them were in that demographic—the group most likely to include mothers of children who might need to be vaccinated.