Ethan Lindenberger, an 18-year-old from Ohio who defied his parents’ anti-vaccination beliefs by getting inoculated, appeared today before Congress to promote vaccine education and outreach campaigns. Lindenberger was one of five people who testified in a Senate committee hearing titled “Vaccines Save Lives: What Is Driving Preventable Disease Outbreaks?” According to experts, the answer is complex — but it’s often centered on a communications gap between medical institutions and parents concerned by vivid conspiracy theories on social media.

Lindenberger opened his testimony with a story that’s gotten wide media coverage: after growing up without inoculation against diseases like measles and polio, he questioned his mother’s claims that vaccines caused autism and brain damage, then began independently catching up on his shots last year. “My mother would turn to anti-vaccine groups online and on social media looking for her evidence and defense, rather than health officials and through credible sources,” he said. “Her love, affection, and care as a parent was used to push an agenda to create false distress, and these sources which spread misinformation should be the primary concern of the American people.”

“Her love, affection, and care as a parent was used to push an agenda.”

This is the second recent congressional hearing about vaccines, held amid a resurgence of measles outbreaks across the country, including a public health emergency in Clark County, Washington. Unlike last week’s House of Representatives hearing, which stalled briefly after audience members shouted at speakers, the mood in the Senate Committee on Health, Education, Labor, and Pensions was calm. Nearly every committee member supported stricter legal mandates for vaccines — although Senator Rand Paul condemned the idea, saying legal force was not “consistent with the liberty our forefathers sought when they came to America.” (Paul noted that he personally supports vaccination.)

But witnesses and senators alike shared chilling warnings about the diseases that vaccinations prevent, and about the dangers of losing social “herd immunity” that protects people who can’t be vaccinated for health reasons. “Vaccines are a victim of their own success,” said Emory University epidemiologist Saad Omer, another witness. Because vaccines reduce disease outbreaks, parents might hear more horror stories about “real or perceived” cases where vaccinations go wrong, and fewer about the actual diseases. So when they’re considering vaccinations, “that mental calculus changes.”

The problem can be compounded by rifts between health care providers and the people they serve. After last week’s House hearing, New Yorker writer Masha Gessen argued that mistrusting the American medical establishment is sometimes “not an unreasonable position,” and that some doctors have historically ignored the real concerns of female and non-white patients especially — making it harder to establish trust with issues like vaccination.

“We have to have employees who reflect the face of the community.”

Today’s Senate hearing framed the issue in more positive terms, describing ways to better connect with communities. “I think the good model is having folks on your staff who are actually culturally diverse,” said Washington state Secretary of Health John Wiesman, who appeared at the hearing. “We have to have employees who reflect the face of the community, and that’s a challenge for a lot of us.” That can help counter anti-vaccination activists who are already building these kinds of local connections, physically visiting groups like the Somali immigrant community around Minneapolis, Minnesota.

Online platforms are under increasing pressure to handle anti-vaccine misinformation on a large scale — US Representative Adam Schiff recently sent letters to Amazon, Google, and Facebook asking why they still hosted it. But during the hearing, witnesses spent more time discussing how to create local support networks that counteract online misinformation, like helping parents who believe in vaccination raise the issue at parent-teacher association meetings.

And although a lot of these projects take place offline, Lindenberger — who turned to Reddit for advice on getting vaccines — says even social media debates were helpful for him. “[My mom] would have this backlash as she would share information — so on Facebook, she would share a video, and people would be like ‘That’s incorrect. That’s false.’ And so as a child, that intrigued me, that people disagreed with my mom.” He acknowledged that someone can’t necessarily be argued out of fears about vaccination. But “addressing misinformation properly can cause change — as it did for me.”