Blima Marcus is an oncology nurse and a member of the ultra-Orthodox community in Borough Park, Brooklyn, where the incidence of measles has risen sharply since last fall, as it has in similar enclaves in the New York area: Williamsburg, Brooklyn; Rockland County in upstate New York; and Ocean County in New Jersey. Health officials have confirmed more than two hundred cases associated with the epidemic; the New York State Department of Health has called it the worst outbreak of measles in the state since the late nineteen-eighties.

When the outbreak began, Marcus’s cousin, who lives in Lakewood, New Jersey, told her that a large percentage of her neighbors were not vaccinating their children. “She asked me to join a text-based chat group to address some facts that were flying around that were just wrong,” Marcus said. False claims, such as the idea that vaccines cause autism, had become entrenched in the ultra-Orthodox community. A pamphlet from a Jewish organization called PEACH (Parents Educating and Advocating for Children’s Health), which is skeptical of vaccines, has been circulating widely; a hotline for the ultra-Orthodox community, called Akeres Habayis (“woman of the home”), also fans fears of immunization. Marcus started spending several hours a day researching scientific studies and answering questions by text. “I was so uncomfortable leaving information out there, with forty women reading it, without actively refuting it,” she says.

Women in the group reached out privately to thank Marcus for her time. They were receptive, she said, because “I wasn’t calling them fools. I didn’t insinuate that anyone was unintelligent. I didn’t accuse anyone of being selfish, and, honestly, I don’t think they are. I think they’re victims of a lot of scare tactics.” In mid-November, Marcus began organizing small group sessions for ultra-Orthodox women, along with colleagues from the Orthodox Jewish Nurses Association, where she serves as the president. The first session was in her cousin’s living room, in Lakewood. I spoke with Marcus last week, by phone, as she ran errands in Brooklyn, about how she approaches these fraught small group sessions and about which strategies she believes are most effective in changing people’s minds. Her account has been edited and condensed.

“I walked in and my cousin had twenty-five chairs lined up in rows, and I said, ‘No, no, no, no, no, no, no!’ We need to sit in a circle. This needs to feel a lot more intimate and comfortable, because I’m talking about the health and safety of their children. The day before I came, everyone in the development got a booklet on their door from PEACH. I guess the organization felt threatened.

“When the women arrived, I asked, ‘Who here hates vaccines?’ and, like, two or three people raised their hands, and I pointed at the door and said, ‘Out!’ For a second, they looked stunned, and then the whole room burst out laughing, and I said, ‘I’m kidding, I’m kidding.’ I showed them that I know we’re going to be disagreeing, but there’s no sarcasm, no heckling, no hollering.

“The session was supposed to be from 8 P.M. to 10 P.M., but it went on ’til two o’clock in the morning. The autism information was mind-blowing to them. There was one study that almost seemed to solidify it for them. It’s a study from Japan. In the late nineteen-eighties, part of the measles, mumps, and rubella vaccine was contaminated, so they replaced the M.M.R. with single vaccines—single measles, single mumps, single rubella—which is what many vaccine skeptics want to do. But, in Japan, vaccination with M.M.R. went down to zero, and autism rates continued to rise in line with every other country. The women liked the graph. They liked the visuals of autism rates going up but M.M.R. administration going down. They saw that the two weren’t connected.

“One woman took four of her kids for the M.M.R. that week. I texted her and said, ‘Hey, how are your children feeling?’ And she said, “They’re O.K. So far they’re not acting autistic.’ And I said, ‘O.K., that’s encouraging.’

“The second meeting we did was in Clifton, New Jersey. The third was in Williamsburg, Brooklyn, right after Hanukkah, in mid-December. For the Williamsburg one, I came with fifty studies or more. I piled them up in front of me and I said, ‘These studies prove that there’s no connection between autism and the vaccines, and this pile proves that the flu shot actually works, and this pile proves that heavy metals have nothing to do with autism.’ I passed around index cards for e-mail addresses, and when I got home I sent out, like, forty studies to people. I learned at the Lakewood one that they want to see the paperwork.

“I give them pointers on how to evaluate research. I say, ‘Look at how many people were enrolled in the study.’ A study with twelve children, that’s nice. But I’m giving you a meta-analysis with 1.5 million children. I say, ‘We need to look at disclosures.’ If you don’t know who’s funding a study, you have to look that up. If you want to find good studies yourself, try Google Scholar, because it’s not going to send you to the anti-vax association. It’s not going to send you to healthnutjob.com.

“It’s hard to change people’s minds, especially when it’s something they’ve been thinking about for so long and when there are horror stories being shared all the time that they have no way of verifying. You also have to address their other beliefs: that everyone is out to get them, that everyone wants to make money off of them. They were shocked to find out that pediatricians locally come home with like a hundred thousand or a hundred and fifty thousand dollars. They thought doctors were millionaires. One woman looked at me and said, ‘Are you trying to tell me that my pediatrician cares about my kid, if he gets sick or not?’ And I said, ‘Of course! Why else would someone listen to screaming children all day for a hundred thousand dollars if they didn’t care?’ They had this very jaded sense of the industry. And that’s where cultural issues come in. There’s a lot of multigenerational trauma, from having been experimented on in the Holocaust and having gotten either no medical care or poor medical care when they lived in eastern European countries and back in the shtetl times. There is also a lot of suspicion of government and whether they care about us little people. The anti-vax propagandists exploit that for all it’s worth.

“Half of what we do is validation. In the ultra-Orthodox community, the average number of children a woman has is around eight. In the U.S. over all, it’s 1.8 children per family. When you have four times as many children in a community, you’re going to see a lot more of everything. They are seeing a lot of autism. There are also a lot of special services available for autism and other kinds of neurodevelopmental issues. The Jewish community is savvy at getting these services and using them effectively. So everyone you talk to has a child getting speech therapy, occupational therapy, special education. We won’t tell you you’re not seeing what you’re seeing. But the reason for it is diagnostic. The diagnostic criteria for neurodevelopmental disorders and autism have widened and widened.

“We need to convince them that vaccines don’t cause injury. They need to believe the data that vaccines are safe. But my closing argument to them is about community. The framework for orthodox Judaism, if you want to live according to the law, is communal. Prayers require a minimum of ten people. We live in close quarters with extended family. So we should consider ourselves especially obligated to prevent harm to our fellow community members. I go through some statistics on immune-compromised children and the number of children who die of infectious disease and have comorbidities like cancer or autoimmune disorders, which make them especially likely to catch and not be able to fight these diseases. And that’s the hardest pill for people to swallow, even the fiercest anti-vaxxers. Because no one wants to think of a seven-year-old with leukemia dying of the chicken pox.”