The long-debunked theory that childhood vaccines cause autism has returned to the spotlight, fueled by the rise of prominent anti-vaccine activists nearly three decades after its initial spread. Where did the “vaccines cause autism” theory come from? Dallas (tca/dpa) – In the late 1990s, a theory gripped parents around the world: What if childhood vaccines — particularly the combined measles-mumps-rubella vaccine — cause autism? Nearly three decades later, the debunked theory has gained renewed prominence in parallel with the rise of Robert F. Kennedy Jr., a long-time anti-vaccine activist who now serves as the US health secretary. Scientists, medical providers and medical researchers are clear on this: Vaccines do not cause autism. To those tuning into the vaccine debate now, it can feel like scientists are dismissing the theory without considering it. But there’s a reason. There has already been a mountain of research investigating vaccines and debunking any connection with autism. Scientists have reached a consensus on this one. Here’s how. Where did the “vaccines cause autism” theory come from? The idea that vaccines cause autism, or at least the popularity of that idea, can be traced to a 1998 research paper. In that paper, then-physician Andrew Wakefield and his co-authors hypothesized that the measles-mumps-rubella vaccine could trigger a combination of gastrointestinal problems and neurodevelopmental “regression” consistent with autism. Wakefield, who is British, published the article in the well-respected scientific journal The Lancet. The paper had a dozen co-authors. (That paper, and Wakefield himself, have since been resoundingly discredited. But let’s take this in chronological order.) The paper, in its initial form, had numerous red flags, including a small sample size of 12 children. Additionally, the paper itself did not claim to actually prove the connection. “We did not prove an association between measles, mumps and rubella vaccine and the syndrome described,” the article says. “Virological studies are underway that may help to resolve this issue.” Even with the original paper’s caveats and limitations, the theory captured the public attention and was simplified to the idea that vaccines cause autism. Researchers and medical professionals have pointed to the paper as one major cause of dropping childhood vaccination rates. The scientific community took note of the paper, too, and responded in the way that science should: By testing the hypothesis again and again. Did other scientists *really* look into Wakefield’s idea? In the years after the Wakefield paper, researchers around the world embarked on studies to look for any link between the MMR vaccine and autism. David Amaral — the founding research director at the MIND Institute at UC Davis, an autism research center — has worked in autism research since the late 1990s, around the same time as the Wakefield paper’s publication. He remembers the flurry of research triggered by the vaccine theory. There was a 1999 epidemiological study in the U.K., published in the same journal that published Wakefield’s paper the year before. There was a 2001 study in California. There was a 2002 study of more than half a million children in Denmark. There was another 2002 study of more than half a million children, this time in Finland. These four examples are just a sampling of the studies on vaccines and neurodevelopmental disorders. There have been many other studies, too. The Autism and Science Foundation has compiled a lengthy list that includes at least 11 additional research studies and analyses related to vaccines and autism. Dr. Jake Scott, a Stanford Medicine professor and an infectious disease specialist, has spearheaded a compilation of randomized controlled trials — which are often cited as the gold standard of research — related to vaccines and vaccine safety. That spreadsheet, Scott wrote in early September federal testimony, has catalogued more than 1,700 studies. “If vaccines caused a wave of chronic disease, our safety systems – which can detect 1-in-a-million events – would have seen it,” Scott wrote in his testimony. “They haven’t.” What did those other studies find? A number of the studies conducted after the Wakefield paper focused on rates of autism among children who had been vaccinated and children who hadn’t. If the MMR vaccine — or another vaccine — did cause or increase the risk of autism, then there should be higher rates of autism among vaccinated children. This was a reality that Wakefield and his co-authors directly addressed in their original paper. “If there is a causal link between measles, mumps, and rubella vaccine and this syndrome,” the paper says, “a rising incidence might be anticipated after the introduction of this vaccine in the UK in 1988.” Scientists and researchers had the same thought. “If there was a link between the vaccines, you should at least see some signal,” Amaral said. “You should see some evidence of it.” But, in follow-up study after follow-up study, researchers found no such evidence. The 1999 UK study authors wrote that their “analyses do not support a causal association between MMR vaccine and autism.” “This study provides strong evidence against the hypothesis that MMR vaccination causes autism,” said the authors of the massive Denmark study. And on and on. The studies repeatedly came back with the same conclusion: No evidence of a link between the measles-mumps-rubella vaccine and autism. That matters because, in the scientific world, a single study cannot prove anything. When a researcher finds a new or important link, other researchers set off on the task of replicating that finding. This is to ensure that the link really does exist, that it wasn’t a mistake by the original researcher, a poorly designed study or simply a fluke. (Spoiler alert: That scientific process also aims to root out deliberate research fraud.) It is only when a finding can be repeated by other researchers that the scientific community reaches “consensus” and agrees that a hypothesis does, indeed, appear to be true. When other researchers set out to validate — or replicate — Wakefield’s study, they couldn’t. It was a death knell for Wakefield’s hypothesis. Dr. Jason Terk, a pediatrician in North Texas, started practicing in 1998, the same year the Wakefield paper was published. “In good faith, the medical community tried to answer the question and it was a very clear answer,” Terk said, “that there was no evidence to support the connection that was raised by this paper.” Even after extensive research, scientists tend to be hesitant to frame anything as an absolute. If there’s a hair’s width opening for a possible other explanation, researchers tend to hedge their statements, to leave room for that extraordinarily unlikely other explanation. In the case of vaccines and autism, though, researchers have come as close to absolute proof as they can. “There is literally no evidence that vaccines cause autism,” said Katherine Meltzoff, a University of California, Riverside professor and autism researcher. “It’s been studied and restudied and restudied almost infinite times since the initial, fraudulent 1998 paper came out.” What happened to Wakefield and his paper? As evidence mounted against Wakefield’s hypothesis and his 1998 paper, The Lancet investigated allegations that the paper’s results may have been fabricated or otherwise manipulated. In 2004, 10 of the 12 co-authors retracted the interpretation of the original data in the paper. Six years after that, the journal retracted the entire article, citing “false” statements in the study, including in how the authors recruited patients. The British medical board, called the General Medical Council, looked into the situation, too. In a report, the council detailed numerous instanc…
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