Amazon appears to be pulling anti-vaccination documentaries from the company's Prime Video service after a US lawmaker urged the tech giant to crack down on the content.

The documentaries Vaxxed: From Cover-up to Catastrophe, Man Made Epidemic, and Shoot' Em Up: The Truth About Vaccineswere previously available on Amazon's streaming service. But on Friday, journalists from CNN and BuzzFeed began noticing you could no longer find them.

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The takedowns occurred after US Rep. Adam Schiff (D-Calif.) sent a letter to Amazon's CEO Jeff Bezos on Friday about the e-commerce giant promoting products and content from the anti-vaccination movement.

"The algorithms which power social media platforms and Amazon's recommendations are not designed to distinguish quality information from misinformation or misleading information and, as a result, harmful anti-vaccine messages have been able to thrive and spread," reads his letter.

So far, Amazon hasn't commented on the congressman's letter or the documentary removals. But the company has continued selling DVD versions of the same documentaries on Amazon's online store, as well as books containing anti-vaccination views.

Schiff's letter demands to know what Amazon is doing to stop vaccine misinformation from circulating over the company's online stores, and whether the e-commerce giant is accepting advertising dollars from activists with the anti-vaxxer movement. "Every online platform, including Amazon, must act responsibly and ensure that they do not contribute to this growing public health catastrophe," his letter adds.

Last month, Schiff also urged Facebook and Google to stop pushing anti-vaccination content to parents. In response, Google's YouTube has pulledadvertising from videos that promote anti-vaccination conspiracy theories. Meanwhile, Facebook said it's preparing more measures to reduce health-related misinformation over the platform. Nevertheless, anti-vaccination groups and content remain available on both platforms, which have tried to balance free speech against charges of censorship.

Pinterest, on the other hand, has reportedly taken more drastic measures and decided to block all searches related to vaccinations over the platform until it can come up with a better strategy to filter out anti-vaccination content.