YouTube, Google's online video hub, has stopped ads from running on videos pushing anti-vaccination, or "vaccine hesitancy," theories as part of its push against misinformation, preventing individuals and groups from making money on the site.

"We have strict policies that govern what videos we allow ads to appear on, and videos that promote anti-vaccination content have been, and remain, a violation of our longstanding harmful or dangerous content advertising policy," a YouTube spokesperson said. "We enforce these policies vigorously, and if we find a video that violates them we immediately take action and remove ads.”

Rep. Adam Schiff, D-Calif., made such a demand to Google in February, after releasing a letter claiming Google had the responsibility to police the spread of misinformation on its search engines and YouTube, due to the massive and growing number of Americans that receive their news from YouTube and other online sources.

"I am writing out of my concern that YouTube is surfacing and recommending messages that discourage parents from vaccinating their children, a direct threat to public health, and reversing progress made in tackling vaccine-preventable diseases," Schiff wrote. "If a concerned parent consistently sees information in their YouTube recommendations that casts doubt on the safety or efficacy of vaccines, it could cause them to disregard the advice of their children's physicians and public health experts and decline to follow the recommended vaccination schedule."

YouTube says that misinformation in and of itself does not inherently violate their community guidelines, but says that the company has taken steps to improve the visibility of "credible" content from verified or trustworthy sources. Content supporting anti-vaccination beliefs is permitted to exist on the platform, but rather than censor, the company instead focuses on uplifting accurate or trustworthy information.

[Related: Facebook considers burying anti-vaccine posts after pressure from Congress]

The sticking point for the company was advertising. Looking at YouTube's guidelines for content safe for advertisers, the top classification of content that is considered "not suitable for most advertisers" is "controversial issues or sensitive ideas." That listing sits much higher than the listings for "sexually suggestive content" and "violence," which also denote unsuitability for advertisers.

The company specifically mentions other conspiracies prevalent on the Internet as examples of "controversial issues or sensitive ideas," including whether the moon landing was real, conspiracies surrounding the Sept. 11 terrorist attacks, whether the Earth is flat, and "miracle cures."

The Department of Health and Human Services has also been proactive in combating anti-vaccination information, having commissioned a 2011 study from a National Vaccine Advisory Committee that encompasses a review of the United States' vaccine safety system. In its first sentence, the report states that vaccines are "one of the most effective public health interventions."

Facebook recently followed suit as well, using similar methods to YouTube. In addition to uplifting trustworthy content, Facebook said it intends to bury pages and posts that "spread misinformation about vaccines" by reducing the "rankings" of the groups and pages responsible and rejecting ads or promoted content that include misinformation or target "vaccine controversies."

YouTube has also started putting a placard attached to the bottom of such videos with a link to the Wikipedia page addressing vaccine hesitancy. The banner, without clicking on it, informs the viewer that vaccine hesitancy is listed as one of the "top ten global health threats" according to the World Heath Organization.

"Users may see information from third parties, including Encyclopedia Britannica and Wikipedia, alongside videos on a small number of well-established historical and scientific topics that have often been subject to misinformation online, like the moon landing," YouTube said in a page linked to a "Why am I seeing this?" prompt.

[Also read: Vaccination controversy puts politicians on the spot]