School was about to start. Doctors at a Pennsylvania pediatric practice wanted to remind parents to get their children vaccinated against human papillomavirus, or HPV, which can cause a variety of cancers. The doctors produced a 90-second video and posted it to the practice’s Facebook page.

The video sparked positive feedback initially and resulted in more parents scheduling appointments for their children and adolescents to get the recommended vaccine. But three weeks later, anti-vaccine activists began inundating the Facebook page of Kids Plus Pediatrics, a Pittsburgh doctors group, with hostile messages.

Within eight days, the page was flooded with 10,000 negative comments from about 800 commenters. Only five were from Pennsylvania. The rest were from across the United States and around the world. Some comments were threatening, such as “You’ll burn in hell for killing babies.” Others were conspiratorial, such as “You have been brainwashed,” the doctors said.

Online attacks against people who speak out in favour of vaccines have become increasingly common, clinicians and vaccine advocates say. Social media websites are the primary platform for the antivaccination movement’s misleading claims. Although anti-vaccine activists are a small minority, on social media they may appear to be the majority.

What made this episode different is that the people at Kids Plus decided to investigate who was behind the attack and how it was carried out.The Pittsburgh practice shared its data with researchers from the University of Pittsburgh Center for Research on Media, Technology, and Health. Researchers analyzed a random sample of nearly 200 commenters to better understand the individuals behind the posts. They analyzed publicly available information that had been posted on each commenter’s Facebook page over two years to examine their social networks. That information included their political leanings and membership in other groups.

Their findings, published Thursday in the journal Vaccine, confirm previous research about those who are opposed or reluctant to vaccinate and the key arguments that resonate with them. Like many who are vaccine-hesitant or opposed to vaccines, the majority of commenters to the Pittsburgh practice were mothers. The top two political affiliations were on opposite ends of the political spectrum, with 56 per cent expressing support for U.S. President Trump and 11 per cent expressing support for Sen. Bernie Sanders, the researchers found.

Among the anti-vaccine themes in the comments were a mistrust of the scientific community, concerns about personal liberty, perceived risks about vaccine safety and the belief that government and pharmaceutical companies are part of a conspiracy to hide information.

Perhaps most significant, doctors and experts said, is that Kids Plus was able to figure out the social media attack was directed from inside closed anti-vaccine Facebook groups. Together with the researchers’ analysis, the information provides the first systematic analysis of how anti-vaccine activists co-ordinate a harmful social media campaign, experts said.

“We know they’re all co-ordinated,” said Erica DeWald, director of advocacy for Vaccinate Your Family, the nation’s largest non-profit dedicated to advocating for vaccinations. “But this is the actual research piece that proves that.”

Many health-care professionals are afraid of the impact anti-vaxxers can have on their business, according to DeWald. The online attacks often result in negative ratings and reviews on sites such as Google and Yelp.

“Quite frankly, it’s created a chilling effect,” she said. “If you’re a new parent trying to find the best provider for your child, because of these false or negative ratings, you could be missing out on finding a really great doctor or provider for your child.”

“This isn’t going away,” said Todd Wolynn, chief executive officer of Kids Plus Pediatrics, referring to online anti-vaccine attacks. “We didn’t want other groups to go through this,” he said. “We said, ‘Let’s learn from this.’ “

Researchers said they did not see any evidence that the comments were posted by bots or trolls. All the profiles they analyzed appeared to be real individuals, said Beth Hoffman, a graduate student who led the research team. The accounts had histories going back many years, over a decade in some cases. There was also evidence that that these real people were “checking in” to real places, having friends, and sharing pictures from real-life events, she said.

Kids Plus Pediatrics is a large practice that has about 20 clinicians and about 20,000 patients in Pittsburgh. On Aug. 23, 2017, the practice posted a video showing some of its providers talking about the importance of the HPV vaccine.

About three weeks later, Chad Hermann, communications director for the practice, received a notification that someone had posted misinformation claiming “the vaccine kills,” he recalled. Within nine minutes, there were three more anti-vaccine comments. Then more six or seven minutes after that. After about 10 minutes, he realized “something new was happening,” he said. The practice had posted videos about vaccine in the past, but they typically drew only a few negative comments.

The next day, the practice started receiving private messages from someone inside a closed Facebook group that launched the attack, he said. That person “would send us screen shots so we could see them co-ordinating the attacks,” Hermann said. In one instance a woman in Sydney directed people to target the practice on different social media platforms. “She would say, ‘Let’s move on to Yelp reviews,’ then change tactics and say, ‘Let’s go after the Facebook reviews,’ “ Hermann said.

Over eight days, the video drew more than 10,000 anti-vaccine comments. Hermann said he banned 838 commenters in the first six days. The comments were not specific to the HPV vaccine. Commenters in the random sample were spread across 36 states and eight countries, including California, Texas, Oregon and Australia, where antivaccination sentiment is strong. Many of the attacks came from a small number of commenters, including some who were posting more than 100 times, Hermann said.

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Researchers found many commenters consistently posted content on Facebook related to “naturalness,” and campaigned against circumcision and water fluoridation. But seemingly opposite groups “cling together on this issue of antivaccination,” said Brian Primack, the senior author who directs the university’s Center for Research on Media, Technology and Health. Other individuals expressed views that focused on liberty and potential government interference.

The pediatric practice said it is taking the information gleaned from the research to put together a primer for other physician practices and a provaccine rapid-response network of physicians and others who will post provaccine information to combat anti-vaccine social media campaigns.

“It will be like a virtual cavalry,” said the practice’s Wolynn. “If somebody is under attack, these will help defend and fight off these attacks.”

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