The site’s terms of service advise people to avoid donating to campaigns that make health claims that have not been “approved or verified by the local or national regulatory body,” however that rule previously was not fully enforced. GoFundMe campaigns either benefiting or being promoted by “vaccine choice” and anti-vaccination groups collected at least $170,000 in donations over the last four years, according to an analysis by The Daily Beast, which first reported the news of the crackdown.

Recent measles outbreaks in Washington, Oregon, and New York, have been linked to the anti-vax movement.

Last week, the American Medical Association sent a letter to executives at Amazon, Facebook, Google, Pinterest, Twitter, and YouTube urging them to help stop the spread of health misinformation on their platforms.

“We applaud companies that have already taken action but encourage you to continue evaluating the impact of these policies and take further steps to address the issue as needed,” Dr. James Madara, head of the American Medical Association, wrote in the letter. “The overwhelming scientific evidence shows that vaccines are among the most effective and safest interventions to both prevent individual illness and protect public health.”

While there is still plenty more work to do, tech giants have started to address the problem of false information about vaccines spreading on their platforms.

Last month, Pinterest said it was blocking all search results related to vaccinations, in an effort to stop the spread of misinformation. Facebook said it would block ads with vaccine misinformation, and would provide users with “authoritative information” about vaccines. YouTube prevents anti-vaccine channels from running ads, which cuts off their income. And earlier this month, Amazon removed Vaxxed, an anti-vaccination series, from Amazon Prime.