You all know about how fake news is threatening your democracy. But there’s another type of misinformation that’s threatening our very health. And this time, people are dying. I’m talking about medical misinformation. Roughly 49 percent of Americans believe in at least one medical conspiracy theory. When people are diagnosed, with cancer and they go online, they’re often hit with absolute falsehoods. These scare patients. And they either delay their conventional treatment or they sometimes reject it. My name is Dr. David Robert Grimes. I’m a cancer researcher. And when a vaccination confidence crisis came to Ireland, my home country, I found myself on the front line. Let me tell you about the human papilloma virus or H.P.V. Every year about 270,000 women die of cervical cancer caused by H.P.V. infection. But for the first time in our history, we now have a vaccine that prevents against it. It’s difficult to overstate how effective this vaccine has been. In America, H.P.V. infection in young girls has dropped about 88 percent. But then things changed. In Japan in 2013, sustained anti-vaccine activism led to a panic, which saw vaccination rates for H.P.V. dropped from 70 percent to less than 1 percent within a year or two. In 2014, a similar outbreak of panic came to Denmark. In the U.S.A., H.P.V. vaccination rates in adolescence remain critically low, hovering at around 16 percent. “The uptake rate for the H.P.V. vaccine has dropped.” In 2015, panic about the H.P.V. vaccine came to Ireland. “For some girls and young women, the side effects of Gardasil go well beyond a few months.” I couldn’t believe that I was hearing, such dangerous falsehoods about a vaccine that prevents 5 percent of all cancers. “We only ever wanted what was best for our girls.” Within a year or so, Irish vaccination rates had gone from highs of 87 percent to about 50 percent. It starts with this: As rational as we like to think we are, and as logical, the truth is that we emote first and we reason later. “And I watched my baby go boom and hit the ground.” You’ll often see a scare story that says — particularly a teenage girl — has had an adverse effect to this vaccination. “I believe with all my heart that the Gardasil vaccination did this to her.” And it’ll be delivered in a very frightening way that captures your attention. “I was such an intelligent girl and now I’ve just got this fog over my mind.” It doesn’t matter that the stories lack any veracity. What matters is they scare us and in scaring us we remember them. And in remembering them, we afford them more weight than they deserve. And so starts a vicious cycle. This explains why lies about the H.P.V. vaccine were able to do so much damage in so many countries. But in Ireland, what really changed the situation was a woman called Laura Brennan. When Laura was 24, she was diagnosed with cervical cancer, and by the time she was 25, that was metastatic noncurable. Laura was alarmed that people weren‘t getting this vaccine that could prevent women from being in the situation that she found herself in. Her campaigning started with a series of advertisements where she talked to parents directly to them. “Protect our future.” She was on talk shows. She was interviewed in magazines. “If anything good comes out of this, I would hope parents would get their daughters vaccinated. The vaccine saves lives. It could have saved mine.” She said, I am the reality of an unvaccinated girl. “So it just shows you how fast and aggressive my cancer is. But yeah, that’s life.” It’s no good just throwing facts of people until you can show them why those facts matter. In Ireland, thanks in large part to her campaigning, rates climbed back up over 70 percent, and are continuing to climb. It shows that you can reverse some of this damage. “When I found out that my cancer was terminal, I wanted to use my voice for good, and for the last 12 months, I haven’t shut up.” Laura exemplified something really, really important: That you never change minds without changing hearts as well. All the journal articles in the world, all the physicians and scientists in the world, saying something is for nothing if you can’t reach people on a visceral emotional level and show them why something matters. I was incredibly honored and privileged to be close to Laura Brennan. She passed away on the 20th of March 2019, aged only 26. But she leaves behind a legacy that will extend far beyond most of our lifetimes. And she will save more lives than a library of journal articles and scientific experts in isolation could ever hope to achieve. And that’s some legacy to leave behind.