Facebook removed personal injury advertisements early this week that contained misleading information about medications designed to prevent the spread of HIV, after months of outcry from LGBTQ organizations like GLAAD, The Washington Post reported. Encouraging people at risk of HIV to take these medications is a key strategy in efforts to reduce the transmission of the virus — so misinformation around this drug is especially concerning. But doctors and public health experts have been concerned for years about the risks posed by similar ads from personal injury lawyers, without the same level of public outcry.

“These types of ads have been ignored for so many years,” says Liz Tippett, a professor studying drug injury ads at the University of Oregon School of Law.

Lawyers spend millions advertising lawsuits that claim people were injured by a drug or medical device company’s products. These ads are often on television and serve as a way to bring in new clients. The ads usually use strong language to highlight the potential harms or risks that come with a particular drug — and that language can affect how risky consumers think a drug or medical device is. Most ads don’t tell viewers to talk with a doctor, and some don’t disclose that they’re sponsored by lawyers.

In this case, the Facebook ads were created by personal injury lawyers bringing lawsuits against pharmaceutical companies that make the medicine PrEP. The ads claim that the medication is harmful. Advocates warned that the ads scared patients away from the preventative drugs, which are considered highly effective by the Centers for Disease Control.

Research shows that these types of personal injury ads make people more likely to think a drug or medical device is risky, and can cause people to be less likely to decide to fill a prescription for a particular drug. In 2017, the US House Judiciary Committee held hearings on the advertising practices, and in 2016, the American Medical Association called for ads to include warnings that patients should speak to doctors about any concerns they have.

But patients haven’t mobilized around the issue before. “It’s very uncommon,” says Lars Noah, law professor at the University of Florida. “It’s never reached the point that a community of patient activists would become alarmed.” That might be because, before this point, advertisements typically didn’t target drugs that were as important for public health as PrEP. “Drugs advertised against to this point were often drugs that were marketed, but weren’t of a high therapeutic value,” he says.

The response to these ads have also clearly focused on patient harm, Tippett says. “In the past, trying to do something about these ads has been viewed as trying to help pharmaceutical companies,” she says. “This is the first really clear example of seeing consumer advocacy as the response.”

The placement of these ads on Facebook brings up additional concerns not seen with television ads, she says: they can be targeted to specific demographic groups, which might increase their potency. Like on television, it’s not clear in many cases that the ads are sponsored by lawyers. “Generally, these don’t contain enough information to help people activate their natural defense mechanisms for this type of information,” she says.

Facebook and other social media platforms are the sites of the next wave of these types of drug injury ads, says Jesse King, assistant professor of marketing at Weber State University. “I think lawyers have been trying to figure out how to get these ads online for a while,” he says. “I’ve heard their use is increasing.”

However, social media may also have made it easier for the community responding to these particular ads to mobilize, Tippett says. “It says who sponsored it, you can trace it back, and Facebook has an ad database. None of that is available when it comes to TV. In some ways, there’s more potential accountability because there’s a paper trail.”

On social media, groups can also run counter advertisements to counteract drug injury ad messaging. Research shows that counter publicity may help to minimize or mitigate the impact ads have on perceptions of drug risk, she says.

The outcry over the PrEP advertisements, and the subsequent response, doesn’t necessarily signal a shift in the way platforms, consumers, and lawyers handle drug injury ads, Noah says. The case is probably an outlier: the lawyers’ ads targeted a highly effective medicine and activated a particularly vocal community in response. He’s not optimistic it will trigger widespread change. “But if it does, and leads to a closer look at the whole category of drug advertising by lawyers, I think that would be wonderful,” he says.