In response to reporting by The Daily Beast, Sen. Bob Menendez (D-NJ) is pressing Facebook on the continued spread of anti-vaccine content across its platform. In a letter addressed to Mark Zuckerberg, Menendez denounces the company's “failure to stem the tide of dangerous myths about vaccinations” and urges the company to be accountable for “harmful lies” that are amplified on its platform.

After a meeting between his staff and the company earlier this month to discuss the topic, Menendez says he remains worried about “gaps” in the way Facebook enforces its rules against ads that spread anti-vaccine and other health misinformation.

Noting The Daily Beast report on anti-vaccine content still thriving on Facebook—and pro-vaccine health info that gets flagged erroneously—Menendez asked the company to provide numbers on how many Facebook users were shown anti-vaccine ads since the platform announced a ban on anti-vaccine content in March of this year. Menendez also demanded to know how many anti-vaccine ads the platform has removed since March and how many legitimate vaccine ads were taken down mistakenly in that process.

In the letter, the senator also cited new concerns around how the platform's hands-off approach to political speech might create a new channel to facilitate the spread of health-related misinformation. In one hypothetical scenario, he asked if a politician could run ads linking vaccines to autism—an example meant to drive home how forbidden content could skirt broader platform rules under Facebook’s controversially laissez-faire new political ads policy.

Under that policy, ads from politicians are exempt from fact-checking, a loophole that could allow health misinformation and other forms of potentially harmful misleading content to further metastasize across the world’s largest social network.