The Lancet medical journal fully retracted a 1998 paper Tuesday that first suggested a link between the measles-mumps-rubella (MMR) vaccine and autism, formally discrediting a key piece of research in the public debate over the vaccine's safety for children.
Multiple studies in the past decade and a review of research on the topic in 2004 by the Institute of Medicine found no scientific evidence the vaccine causes autism in children, but concerns have persisted among consumers and broadened to other vaccines as well.
"It's hard to unring the bell," says Paul Offit, chief of infectious diseases at Children's Hospital of Philadelphia. Offit has long encouraged parents to continue vaccinations amid the public debate over vaccines and autism. He is also co-inventor of a rotavirus vaccine. "That initial publication [in the Lancet] gave birth to the notion that vaccines can cause autism."
The original study examined 12 children in Britain and put forth the hypothesis that the MMR vaccine could be a cause of autism. In Britain, MMR vaccine coverage dropped sharply -- from 92 percent in 1995 to 84 percent in 2002, after the publication of the study. The country has experienced several large measles outbreaks since then.
The British journal's decision to retract the research came after the United Kingdom's General Medical Council's ruling last week that the researchers acted dishonestly and unethically, including carrying out unnecessary invasive tests on children and being paid by lawyers of parents who thought their children had been harmed by the vaccine.
Among its findings on the study's improper practices, the Council's report stated that lead author Andrew Wakefield took blood samples for research from children at his son's birthday party, and paid them each about $8.
Ten of the 13 authors of the original paper partially retracted it in 2004, but Wakefield did not, and the Lancet declined to fully retract the paper at the time. Lancet's editor, Richard Horton, told the Wall Street Journal Tuesday, there wasn't enough "evidence back in 2004 to fully retract the paper but we did have enough concern to persuade the authors to partly retract the paper."
Neal Halsey, director of the Institute for Vaccine Safety at the Johns Hopkins Bloomberg School of Public Health, said the scientific basis for a retraction had been evident for years.
"There were so many problems associated with that study it should have never been published," says Halsey.
More than 20 studies have been conducted since the Lancet study that show there is no association between the MMR vaccine and autism, and no studies have been published in peer-review journals that support the idea, Halsey says.
"It's very important that the article was retracted because it validates that the material that was submitted for publication was not based on good science," he says. "I hope that those parents who still have some apprehension and uncertainty in their minds about MMR will now feel more comfortable having their children immunized and immunized on time."
But the decision seems unlikely to settle what has turned into something of a national feud between U.S. public health officials imploring parents to have their children immunized and parents and consumer advocates, who say they have the right -- and the duty -- to question the possible effects of vaccines on their children.
Sara Difucci, a coordinator for Talk About Curing Autism, a support organization for families with autistic children, said the Lancet decision will not, and should not, affect parents’ concerns about vaccines because there is still so much research that needs to be done on the issue.
“People are not going to have confidence in the MMR vaccine until [researchers] explore the possibility of subsets of children having an adverse reaction,” Difucci said.
Groups like hers considered the 1998 study important, but point to other evidence, like the rising rates of autism in children — an average of 1 in every 110 children in the United States had some form of autism in 2006, up 57 percent from 2002, according to the Centers for Disease Control and Prevention — and the ever-growing vaccine load that parents are advised to give their children.
Mistrust of vaccines also grew in the late 1990s because of thimerosal, an additive containing mercury that had been used in many vaccines for decades. The U.S. public health agencies decided in 1999 it should be eliminated as a precautionary measure because of “the widely acknowledged value of reducing exposure to mercury,” wrote the CDC, though the agency says the low doses of the preservative used in vaccines were never shown to be harmful. Nearly all immunizations for children have been thimerosal-free since 2001.
Then in 2008, a case brought by the family of Hannah Poling, an autistic child from Georgia, to the National Vaccine Injury Compensation Program was made public. In that case, the U.S. government agreed to compensate the family on the theory that vaccines may have aggravated a rare underlying illness that may have predisposed her to symptoms of autism. Julie Gerberding, then-head of the CDC, denied that the case had any greater implications and told a press conference, "This does not represent anything other than a very special situation."
“Let me be very clear that the government has made absolutely no statement indicating that vaccines are a cause of autism,” Gerberding said at that time, according to media accounts.
But the case only furthered suspicion among some parents and in June 2009, the National Vaccine Advisory Committee endorsed further study of links between vaccines and autism in subpopulations, acknowledging that “a small and specific subset of the general population (such as those with mitochondrial dysfunction) may be at elevated risk of reduced neurological functioning, possibly including developing ASD [Austism Spectrum Disorder], subsequent to vaccination.”
Difucci says that, regardless of these developments, she still sees an “unwillingness of mainstream medicine to explore the hypothesis” put out by the Lancet study. She added that this is particularly painful for many parents, including herself, who watched their own children go from normally developing toddlers to showing signs of autism.
“This is a legitimate scientific question,” says Barbara Loe Fisher, president of the National Vaccine Information Center, another advocacy group. “[The retraction] sends a signal to the rest of the scientific community that when you dare to investigate the link between vaccination and autism, you do that at your own professional risk.”
Offit says it is unusual for a journal to retract a study because usually it would fade away if the science is never reproduced, which, in the case of the 1998 Lancet study, it wasn't. The study's staying power is why the retraction is important, he said, adding that he hopes the Lancet's decision will send "a strong message that there was nothing to this science."
However, according to Offit, it is easy to scare people, but not so easy to convince them that something is safe.
"I do think there are people who have come to believe that vaccines cause autism and that belief will not be shaken until there is better data that show the real causes for autism," Offit says. "Maybe that's the only way this ends."
Editor's Note: Watch an interview with New York Times public health reporter Gardiner Harris on the vaccine story and find a link to reporting on Wakefield's response to the Lancet's retraction on this Rundown blog post.