Anti-vaxxers couldn’t be happier about the controversy surrounding Planned Parenthood’s fetal tissue donation programs. Many in the anti-vaccine movement have long maintained that fetal tissue in vaccines is behind increasing rates of autism, even though vaccines do not contain fetal tissue and rates of autism might not be rising after all.

But the anti-vaccine movement isn’t just piggybacking on David Daleiden’s undercover sting investigation into the women’s health provider. One of its icons tutored him.

The California 26-year-old behind the Center for Medical Progress (CMP), an organization that has so far released two videos alleging to show Planned Parenthood officials discussing the “sale” of fetal body parts, has been selective with his media appearances. This marks the fourth consecutive article for which Daleiden did not provide comment to The Daily Beast.

But an interview with Daleiden in the National Catholic Register revealed this crucial detail: “Theresa Deisher helped to prepare [him] for his role as a biomedical representative, teaching him the ins and outs of the field.” Deisher, who did not respond to request for comment, is one of the chief proponents of the debunked theory that fetal DNA in vaccines is linked to autism.

For Daleiden, a man who, as The New York Times noted “only reluctantly talk[s] about himself,” the link to Deisher is one more clue about his background and the origins of his investigation. Daleiden has already been linked to a retinue of far-right activists—including the militant pro-life group Operation Rescue, which is partially funding the CMP—but his training under a noted vaccine skeptic has not yet been brought to light.

In a 2009 article for the American Life League, Deisher laid out her theory, arguing that the introduction of a new combined measles, mumps, and rubella (MMR) vaccine in the late 1970s—a vaccine that was developed, in part, through fetal tissue research—could be “an environmental trigger for autism.”

It’s an idea that Deisher believed so strongly that she left a more traditional biotech career behind to found AVM Biotechnology—which her CV describes as “the marquee prolife biotech company worldwide”—as well as the Sound Choice Pharmaceutical Institute (SCPI), which “promote[s] consumer awareness about the widespread use of electively aborted fetal material in drug discovery, development, and commercialization.”

SCPI is currently raising money to develop an “ethical vaccine” to act as an alternative to Merck & Co’s MMR-II vaccine, the only licensed MMR vaccine in the United States. The SCPI website describes the organization’s theories about the dangers of current vaccines in more detail:

“In 1979 we started injecting our children with vaccines that are contaminated with aborted fetal DNA fragments and a retrovirus, and autism began to rise. Then we added more jabs with aborted fetal vaccines and thimerosal, which can also cause DNA breaks, to vaccines in 1988, and autism rose more. Then in 1995, we added much more aborted fetal DNA contaminants to the chickenpox vaccine, and autism really rose.”

Deisher was also the lead author on a 2014 paper in the Journal of Public Health and Epidemiology (PDF) which advanced a similar correlation: “In 1979, coincident with the first autism disorder change point, vaccine manufacturing changes introduced human fetal DNA fragments and contaminants into childhood vaccines.”

The study was perceived as a win by the anti-vaccine movement and the pro-life movement alike, but it was widely discredited in the scientific blogosphere, even by Deisher’s fellow Catholic scholars.

“[D]eeply held beliefs do not make for rigorous scientific inquiry. And pro-life parents seeking to do the best by their children and by their culture deserve better than to have a plausible sounding lie masquerading as truth,” wrote one.

Pro-life media outlet Life News published on SCPI’s previous research in 2010 and it was also discredited then, too. As Yale neurologist Steven Novella explained at the time, the viruses in some vaccines are indeed cultured in two “human diploid cell lines” originally derived from fetal tissue in 1964 and 1970, respectively. Both cell lines—WI-38 and MRC-5—are over 40 years old and “the cells themselves are not part of the vaccine.”

In other words, vaccines do not contain fetal tissue.

According to a 2015 CDC vaccine summary (PDF), only a handful of vaccines are cultured in cell lines derived from that original fetal tissue—most notably MMR, varicella (also known as chickenpox), and hepatitis A vaccines.

To be clear, however, although many in the anti-vaccine movement colloquially claim that vaccines contain “aborted fetal tissue,” Deisher’s particular hypothesis is that fetal DNA is the culprit.

But in February of this year, when pro-life objections to vaccination surfaced in the mainstream media, Paul Offit, the director of the vaccine education center at the Children’s Hospital of Philadelphia told ABC News, “There are perhaps nanograms of DNA fragments still found in the vaccine, perhaps billionths of a gram. You would find as much if you analyzed the fruits and vegetables you eat.”

Novella also clarified in his debunking that viruses in vaccines do “come away with bits of DNA from [the] cell line” as a function of viral replication but that “[t]here is nothing special or different about this DNA.”

“There is no theoretical reason why it should pose any health risk,” he concluded. “This is simple scare-mongering using deception and misinformation.”

To sum up: Not only is residual fetal DNA in vaccines not linked to autism, several studies have confirmed that vaccines as a whole are not tied to autism, and, according to a new study in the American Journal of Genetics, the recent spike in autism diagnoses may be due to the rampant “reclassification of individuals with related neurological disorders” as autistic, rather than to any significant increase in the incidence of the disorder itself.

But science hasn’t stopped some segments of the anti-vaxx crowd from fanning the flames of the recent Planned Parenthood controversy. Children of God For Life, a pro-life vaccine truther organization cheered Deisher’s involvement in Daleiden’s investigation, writing on their Facebook page: “God bless Dr. Deisher for her help in exposing Planned Parenthood!”

Life Site News, a prominent pro-life media outlet, used the Planned Parenthood news to provide a platform to Children of God For Life Executive Director Debi Vinnedge, who believes that abortions have been performed for the express purpose of developing vaccines despite CDC statements to the contrary.

Some conservative corners of social media have also witnessed an inscrutable mix of anti-vaxxers trying to recruit pro-lifers by using fetal tissue as a talking point and pro-lifers trying to recruit anti-vaxxers into the fight against Planned Parenthood.

These two groups appear to exist in something of a Venn Diagram formation: some anti-vaxxers oppose all vaccines, some pro-lifers only oppose vaccines derived from fetal cell lines, with some pro-life anti-vaxxers occupying the intersection.

Some of the most influential anti-vaxx Twitter accounts on the #CDCwhistleblower hashtag—as analyzed by Wired in June—have also been weighing in on the Planned Parenthood debate.

The intensity of this scandal could breathe new life into the theories about vaccines, fetal tissue, and autism that still manage to circulate in pro-life and anti-vaccine circles despite a lack of scientific evidence. Trained by a pro-life vaccine skeptic, David Daleiden has not only done damage to Planned Parenthood’s public image, he has drawn renewed attention to one of anti-vaxxers’ favorite topics.