Fifteen miles west of Minneapolis, a billboard looms over a field of tall grass beside Highway 55. The sign features a photo of Evee Clobes, a baby girl with sparkling eyes, flushed cheeks and an expression frozen in wonder. Next to her face are the words, "HEALTHY BABIES DON'T JUST DIE." The web address of a group opposed to mandatory vaccinations is at the bottom.

Since her death in March, Evee has served as a literal poster child for the anti-vaccination movement. Her face and chunky legs — adorned with Band-Aids from her shots — are featured on anti-vaccination websites and billboards. The story of her death is told at protests, read aloud at statehouses, and offered up by her mother and other activists as proof of the horror vaccines can bring.

Evee's story, as her mother Catelin Clobes tells it, is of a healthy 6-month-old who died 36 hours after a checkup where she got several vaccinations. Clobes and an army of online activists now say the vaccines caused Evee's death. That belief, and Clobes' willingness to make Evee part of a national media campaign, have turned the grieving mom into a rising star in the anti-vaccination world. Her Facebook posts draw hundreds of thousands of views, and multiple fundraisers set up by anti-vaccination activists on her behalf have raised tens of thousands of dollars. She has become a champion of other anti-vaccination parents around the country.

But there's a problem with the story at the heart of this crusade, and with Clobes' new role as an anti-vaccine heroine. Her local medical examiner has ruled that the evidence — collected in an autopsy and by first responders — shows Evee accidentally suffocated while co-sleeping with her mother.

Anti-vaccination activists have long targeted their message to parents of autistic kids. They have also, however, pursued another vulnerable population of parents searching for answers — mothers and fathers of babies who have died unexpectedly, especially when the deaths are linked to Sudden Infant Death Syndrome, or SIDS. At a time when the U.S. faces the largest outbreaks of vaccine-preventable illnesses in decades, a network of activists is finding new recruits to the anti-vaccination cause by raising questions about the sudden deaths of several dozen babies and young children.

That network includes discredited physician-turned-anti-vaccination celebrity Andrew Wakefield, whose retracted study popularized the false belief that vaccines are linked to autism; Del Bigtree, a former "Dr. Phil" producer who runs the country's most well-funded anti-vaccine nonprofit, Informed Consent Action Network; and social media activist Larry Cook, who hosts the largest and most active anti-vaccination community on Facebook.

Since 2018, Cook has published at least 20 different articles alleging a baby's death was the result of a vaccination — despite official, medically supported explanations that include SIDS, pneumonia and accidental asphyxiation. Clobes joined Cook's group after Evee died, and her story is among Cook's 20.

Stories like Evee's are "incredibly common and very effective," said Naomi Smith, a lecturer at Federation University Australia who has studied the anti-vaccination movement. "Anti-vaccination communities have long favored this type of personal testimony to get their message across. These stories are also presented as being more meaningful and more 'real' than official statistics."

"They [hit] that core fear parents have about keeping their children safe," Smith added.

And as public health officials work to contain outbreaks of preventable diseases like measles and social media platforms crack down on vaccine misinformation, Clobes serves another purpose for the anti-vaccination community. Testimonies like hers don't just drive billions of views to anti-vaccination websites or raise millions for the cause, they also provide a kind of human shield. Who wants to pick a fight with a grieving mother?

How Evee's story spread

Catelin Clobes spent the night of Feb. 28 as she did most others — with Evee. Clobes breastfed Evee to sleep and set her down in the queen bed they shared, according to the Wright County Sheriff's report. Clobes then had a whiskey cocktail, watched some basketball and, a few hours later, lay down beside Evee, according to the report.

When Clobes woke up the next morning, Evee didn't stir and she was cold to the touch, Clobes told investigators.

Distraught, Clobes called 911. "This can't be real," Clobes told the operator, according to a transcript of the call. "This is because she was sleeping with me."

According to reports by a detective who examined Evee at the scene and the medical examiner who performed Evee's autopsy, the skin on Evee's face had creases that looked like they could have come from a blanket. Areas of her nose, chest, arms and legs were discolored and pooled with blood, indicating Evee had been face-down for some time.

The medical examiner initially found the cause of death to be "undetermined," with co-sleeping with an adult as a "significant condition." Three months later, at Clobes' request, the same examiner reviewed the case and amended the cause of death to positional asphyxia, or suffocation.

"There are no scene or autopsy findings and no scientific literature to support vaccination as a cause of, or contributor to, Evee's death," the Wright County medical examiner, Dr. A. Quinn Strobl, wrote in a June letter explaining the official change to Clobes.

Clobes rejected these findings in an interview with NBC News.

"I safely co-slept with my daughter, that has nothing to do with her death," she said via Facebook Messenger.

The day after Evee died — before the medical examiner had issued any findings — Clobes started pouring out her heartbreak and confusion on Facebook.

"This feeling of pain is indescribable," Clobes wrote next to a video of Evee laughing that has now been viewed over half a million times and attracted 3,000 comments. "The unanswered questions of how or why make it worse."

Clobes' grief and Evee's giggle were like a siren, attracting dozens of family and friends, and then hundreds and thousands of strangers offering condolences in the comments.

Within hours of her post, some had answers.

"Vaccine injury is real and a movement is spreading across the nation," one woman wrote. "Organizations are filled with people and parents who understand what you are going through and can help offer guidance and support to you."

Some posters added links to Stop Mandatory Vaccination, a website founded by Larry Cook, a man without medical training who has made a name as a leader of the online anti-vaccination movement.

The links posted to Clobes' timeline were testimonials and interviews featuring mothers who suggested their children had been irreparably injured or killed by vaccines, pages that make up the most popular and engaged-with section of Cook's site.

Within a week of her daughter’s death, Catelin Clobes joined Larry Cook’s Stop Mandatory Vaccination Facebook group. via Facebook

Cook's isn't the only site to publish these stories, though its posts are the most widely shared. Other websites, including Vaccine Choice Prayer Community and Circle of Mamas, post similar allegations.

Since 2015, Cook has made a business out of the anti-vaccination narratives of distressed parents. He has raised over $100,000 through multiple GoFundMe campaigns and then via other platforms after GoFundMe banned him in March. Cook has his own Amazon storefront, where he promotes anti-vaccine books and films, taking a cut of the sales, and raises an unknown amount through his website, accepting donations through PayPal that "go directly to me," according to his website.

"I and I alone decide how to use the funds," says the site. Cook says the money has funded anti-vaccine ads, advocacy and "secret projects." He's currently weighing the launch of a dating site for people with anti-vaccine views. Cook did not respond to multiple requests for comment.

Clobes seemed open to the anti-vaccine messages aimed at her. A day after her initial post, she was attaching updates, urging others with stories of health scares after infant vaccinations to get in touch.

Within a week of her daughter's death, Clobes had joined Stop Mandatory Vaccination's 169,000-member closed Facebook group, filed a report with the Vaccine Adverse Event Reporting System, the federal government's vaccine safety surveillance program, and retained a lawyer. The Stop Mandatory Vaccination website published an article about Clobes.

The next week, a local activist helped Clobes set up a fundraiser through GoFundMe with the goal of raising $5,000 for a "private autopsy" and other expenses related to Clobes' quest for answers. (Clobes has received more than $22,000 and has raised the goal to $40,000.)

For the autopsy — more precisely, a study of tissue samples retained by Wright County — Clobes' lawyer hired Dr. Douglas Miller, a clinical professor of pathology at the University of Missouri and one of the few mainstream medical professionals anti-vaccination activists seem to respect. He has served as an expert witness for parents who filed lawsuits claiming vaccines triggered SIDS in their children. Clobes said on social media that Miller would be doing the study.

Miller, who charges $500 per hour to evaluate a vaccine injury claim case, confirmed to NBC News that he completed an evaluation for Clobes in July.

Miller said his investigation found no evidence that vaccines had contributed to Evee's death. He said he told Clobes of his conclusion, and had declined to support her case in the federal government's National Vaccine Injury Compensation Program, known more commonly as Vaccine Court. He declined to name the factors that led to his decision, citing concern for Clobes' privacy.

Online, however, Clobes claimed Dr. Miller's report offered "proof" that Evee had suffered "a cellular infiltration triggered by an immune response from the vaccinations."

In an email to NBC News, Miller said the neuropathologist Clobes referred to "was not me, if he or she actually exists."

"I did not tell Ms. Clobes of any such finding," Miller said, "and I did not provide her or her attorney with any report which alleged any such finding."

When asked about Miller's statements, Clobes directed questions to her lawyer, who did not return multiple requests for comment.

Clobes continued, and expanded, her advocacy after receiving Miller's report. In August, she registered the Justice For Evee Organization as a nonprofit in Minnesota and began soliciting donations. Through her website, Clobes also sells Evee-themed merchandise, including T-shirts, bumper stickers and pins, with proceeds slated to go to anti-vaccine advocacy in Minnesota and beyond.

An Evee Clobes billboard west of Minneapolis. NBC News

But Clobes isn't just telling her own story. She's using her growing platform to circulate the stories of other families who claim vaccines killed their babies. Since Evee's death, Clobes has posted on Facebook about seven other babies who unexpectedly died, tagging their mothers, and sharing the story with her followers, who now number more than 11,000. She started GoFundMe campaigns for two of the mothers.

A separate Evee-branded campaign was launched by Health Choice Minnesota, the local arm of American Citizens for Health Choice, a national anti-vaccine organization that raised nearly half a million dollars from 2012 to 2017, according to federal tax returns. Health Choice Minnesota paid for two Evee billboards outside Minneapolis, and the signs steer onlookers to the group's website, which has a donate option "to fund legal fees as well as public education & support campaigns."

A representative for Health Choice Minnesota declined to answer questions about the money raised by the Evee campaign. "We confirmed the details and provided support," said the representative via Facebook. "Every family deserves respect and support after the loss of a loved one."

Health Choice's founder, anti-vaccination advocate and state Republican Party finance chair Jennifer Larson, also co-founded the Vaccine Safety Council of Minnesota, which made news earlier this year for promoting anti-vaccination theories among the local Somali-American population. Larson did not respond to a request for comment.

In September, Clobes appeared on nationally known anti-vaccination advocate Del Bigtree's online talk show, "The HighWire." Clobes hinted she might sue the Wright County medical examiner over a "cover-up." Bigtree interspersed his interview with Clobes with home videos of Evee and a re-enactment of her death.

In an interview with NBC News, Bigtree dismissed the suggestion that claims like Clobes' deserve extra scrutiny.

"All I'm doing is letting her tell her story," said Bigtree, whose nonprofit brought in $1.4 million in revenue in 2017— more than any comparable group. He compared his work to media coverage of the #MeToo movement, in which women have made sexual assault allegations against powerful men. "Are we not supposed to listen to the women?"

Over Facebook Messenger, Clobes said she came to her beliefs on her own and wants others to do the same.

"I'm not out on this big 'anti-vaxx' wagon, to deceive people," she wrote. "I'm just telling my truth. What happened to my daughter. How much I loved her. How much this has broken me."

'I just want the truth out there'

Evee isn't the first baby whose face has been enlisted in the anti-vaccination cause. Nicholas Catone, a 20-month-old who died in 2017, was featured in a 30-billboard campaign last year from Learn The Risk, a California-based national nonprofit that claims to expose the risks of vaccines. His parents are unsatisfied with the official finding of a "sudden, unexplained death," and instead blame a vaccine given three weeks earlier.

Sometimes, a baby becomes a face of the movement without both parents' consent.

Mark Cooney, 30, lost his daughter, Sophia, in February.

Cooney describes Sophia as a happy 2-month-old, with her mother's blue eyes and sandy blond hair. The night Sophia died, Cooney came home from work to find his girlfriend and Sophia's mother, Laura Stanard, asleep on the couch in their Fort Collins, Colorado, apartment. He called 911 when he saw his daughter.

Mark Cooney with his daughter Sophia. Courtesy Mark Cooney

Sophia was "found in a supine position," with her head "pushed into an area between two cushions" on the couch, the Larimer County coroner's report reads.

Cooney told NBC News that Stanard "pulled Sophia from in between her and the cushion but the baby was purple and limp."

Cooney performed CPR, but neither he nor paramedics could revive Sophia. She was pronounced dead at the hospital.

Sophia's death was an accident, caused by "asphyxiation due to being in a compromised position while co-sleeping," according to the coroner's report. "The mother breastfed her on a sofa, and unfortunately fell asleep with her still in her arms."

According to the police report of the incident, a detective "asked Laura what she thought happened and Laura said she believed Sophia suffocated against the back of the couch. Laura said this was her fault because she fell asleep with her. Laura began to cry."

In the report, the detective wrote that Stanard said she had smoked marijuana that morning and afternoon, which is legal in Colorado. The detective wrote that a doctor consulted about the incident said the use of alcohol or marijuana "would make co-sleeping unsafe."

After Sophia's death, Cooney said he couldn't work. He and Stanard broke up, and soon after, Cooney moved to Las Vegas, then back home to Nebraska.

On the six-month anniversary of Sophia's death, Cooney saw that a stranger named Catie Clobes had posted a GoFundMe campaign to Facebook, asking for donations to help Stanard with "bills and expenses" after Sophia's death. Sophia is one of six babies in as many months whose deaths, without medical evidence, Clobes has promoted to her 10,000 followers and various Facebook groups as vaccine-related. Articles about Sophia soon followed on websites like Stop Mandatory Vaccination, which posted the story with the headline, "Infant Dies 14 Hours After Receiving 8 Vaccines." The article is one of the site's most popular this year, getting some 57,000 Facebook likes, comments and shares, according to a Buzzsumo analysis.

When he saw the posts, Cooney said: "I couldn't breathe. It's like someone was making a mockery of my precious little Sophie."

Cooney asked Stanard, Clobes and then GoFundMe to take down Sophia's campaign, and when those requests were ignored, he contacted the Fort Collins police, who opened an investigation into the GoFundMe account. After Cooney, friends and family loaded the campaign's comment section with complaints, it was taken down, having raised just $225. No charges were filed.

Stanard said in a brief conversation over Facebook Messenger that she had approached Clobes after seeing her story on Facebook. "I chose to reach out because who wouldn't reach out to someone who went through the same thing?" Stanard said. "Everyone just wants to find someone to relate to and I finally found someone who actually believed me."

Cooney doesn't blame his ex for convincing herself that vaccines killed Sophia, but he is angry just the same.

"I just want the truth out there: Babies asphyxiate, this happens," Cooney said. "These anti-vaccination people are continuously contacting parents who have lost children, giving them false information and false hope. This stuff is wrong."

'Where's the proof?'

Clobes calls Evee a "superhero" for her posthumous role in the anti-vaccine movement. On her Facebook page, Clobes posts screenshots of messages from parents who, she says, have seen her story and been persuaded not to vaccinate their children. The Catones post similar images along with the hashtag #onestarfishatatime, a reference to an inspirational story in which a boy, faced with a beach of dying starfish, saves as many as he can, one by one.

While it's impossible to measure the impact of these stories on vaccination rates or public opinion, it's safe to say they've been seen and shared millions of times.

The overwhelming majority of parents in the United States vaccinate their children, but a growing number do not. This hesitancy has contributed to the biggest resurgence of measles in decades, leading public health officials to sound the alarm and counter online vaccine misinformation with their own message: Multiple studies and scientific reviews have shown that while serious reactions from vaccines are possible, they are extremely rare. Grieving parents may believe vaccines caused their baby’s death, but the timing is often a coincidence, since any baby who dies would likely have been vaccinated recently.

The latest venue for Evee's story has been California, where anti-vaccination activists have been protesting legislation that closed medical exemption loopholes in the state's vaccine law. This month, Clobes posted in opposition to the bill, sharing a photo of Evee in her casket alongside a claim that there's been "a huge cover-up" surrounding her death.

Last week, California state Sen. Richard Pan, a pediatrician who led the bill's push, got into a Twitter spat with the actor Rob Schneider, who argued against the legislation by sharing Clobes' post.

"Catie has my sympathy for the loss of her daughter Evee," Pan replied to Schneider on Twitter. "Blaming her death on vaccination requires proof."

Pan's remarks were seized on as heartless by Clobes' supporters, who accused him of attacking a grieving mother.

But Pan, who has been harassed, physically assaulted and most recently targeted by an anti-vaccination advocate who poured a red liquid on the California Senate floor, says sympathy shouldn't trump science when it comes to decisions that can affect public health.

"It's one thing for a family to say, 'My child died,'" Pan told NBC News. "But when you say, "It was caused by vaccines, and now I want to change laws or stop laws in a way that will hurt children,' then it's not inappropriate to say: 'Where's the proof?'"