Amazon is under fire again for helping spread anti-vaccine conspiracies.

Four major anti-vaccination groups -- National Vaccine Information Center (NVIC), Age of Autism, Learn the Risk, and Physicians for Informed Consent -- are raising money through the Amazon’s charity fundraising program, AmazonSmile, according to a reportby The Guardian.

Other anti-vaccine organizations such as American Citizens for Health Choice (ACHC), A Voice for Choice, Informed Consent Action Network, and the National Health Freedom Coalition are also included in the program.

Through AmazonSmile, customers can choose to donate 0.5 percent of their purchase price to a charitable group of their choice when shopping with Amazon. The fundraising initiative has donated more than $100 millionto organizations such as St. Jude’s Children’s Hospital, Doctors Without Borders, and the ASPCA since it launched in 2013.

It’s unknown just how much anti-vaccination groups have raised through the program. As the Guardian points out, many of these organizations have an operating budget in the five to six figures. NVIC, the largest of these nonprofits, had more than $1 million in revenue in 2017.

These groups have promoted dangerous conspiracy theoriesabout the safety of vaccinations, such as the belief that vaccines cause autism, which have thoroughly been debunked by scientists and medical professionals.

The Guardian report also uncovered how individuals within the anti-vaxxer movement are also raising money through Amazon’s Influencer program.

Amazon has recently undergone similar scrutinyover documentaries promoting the anti-vaxxer movement found on Amazon Prime. Last Friday, United States Rep. Adam Schiff sent a letter to Amazon CEO Jeff Bezos blasting the company for spreading misinformation about vaccines. In his letter, the congressman demanded to know what the company was going to do about the anti-vaccination content.

Anti-vaccination documentaries, such as Vaxxed: From Cover-up to Catastrophe, were later removed from Amazon Prime.

"Every online platform, including Amazon, must act responsibly and ensure that they do not contribute to this growing public health catastrophe," stated Schiff in his letter.

Last month, Facebook, YouTube and other social media platforms faced its own issues with the anti-vaccination movement.

A recent report uncovered how anti-vaccination conspiracies were proliferating on Facebookthrough private groups. A separate report also exposed a similar rise in anti-vaxxer content on YouTube. The company responded by demonetizing anti-vaccinationvideos on the platform.

Pinterest has possibly taken the most extreme measures against the anti-vaxxer movement of any major social media platform. The company recently started blocking searchesrelating to vaccine misinformation on its website.

Mashable has reached out to Amazon for comment and will update this post when we hear back.

UPDATE: March 5, 2019, 1:16 p.m. EST An Amazon spokesperson sent Mashable the following statement:

“Charitable organizations must meet the requirements outlined in our participation agreement to be eligible for AmazonSmile. Organizations that engage in, support, encourage, or promote intolerance, hate, terrorism, violence, money laundering, or other illegal activities are not eligible. If at any point an organization violates this agreement, its eligibility will be revoked. Since 2013, Amazon has relied on the US Office of Foreign Assets Control and the Southern Poverty Law Center to help us make these determinations.”

UPDATE: July 29, 2019, 1:36 p.m. EDT A lawyer from Physicians for Informed Consent (PIC) has contacted Mashable to dispute characterization of their organization as "anti-vaccination." Per the lawyer, PIC is "ethically opposed to the coercion of vaccination." The organization is "pro-informed consent" for vaccinations; their objection is to "vaccine mandates."

Mashable uses the label "anti-vaccination" to refer to groups that question the safety and effectiveness of vaccinations, and/or advocate for non-medical exemptions to vaccination. Per PIC's website, "PIC’s vision is to live in a society free of mandatory vaccination laws."