Vaccines and autism: there's no link

- October 31, 2008

Susan Bryson holds Dalhousie's Joan and Jack Chair in Autism Research. (Danny Abriel Photo)

She seemed to be everywhere. Last fall, actress Jenny McCarthy could be found on a host of American talk shows, including Larry King Live, The View and The Oprah Winfrey Show promoting her book Louder than Words: A Mother’s Journey in Healing Autism. During the Oprah appearance, she made several controversial claims, including the idea that vaccines had a role to play in causing her son’s autism. “The nurse gave (Evan) the shot... and soon thereafter—boom—the soul’s gone from his eyes,” she said.

Seen by millions of Oprah viewers, hers was a compelling story, presented passionately and articulately. But was she right? “I’m just a mom,” she said, adding she received her degree from “the University of Google.”

Despite the lack of credible scientific evidence establishing a connection between vaccines and autism, debate rages on. The controversy seems to be everywhere, fuelled by celebrities, bloggers, websites and the mainstream media. With autism rates continuing to rise (estimated at one child in 166), now more than ever parents are finding themselves confused and doubtful about whether to vaccinate their children.

What should parents believe? Is there a connection between autism and vaccines?

“We don’t want to close our minds to further research and inquiry, but we really need to treat the vaccine-autism connection as highly speculative,” says Susan Bryson, Dalhousie’s Joan and Jack Craig Chair in Autism Research, and one of the world’s foremost autism experts.

“We should still ask questions and seek answers, but in the meantime, we need to follow paths that are evidence-based and make sense theoretically,” she says. “Especially when we are considering what the priorities are for focusing our attention and money.”

While experts say there is no reliable way to track the impact of the controversy on Canada’s vaccination rates, in other countries like Britain, MMR (measles, mumps and rubella) vaccination rates plummeted from 95 to 75 per cent (although that figure has begun to recover). The British outbreak of these diseases can be traced directly to one of the only studies that suggested a link between autism and vaccines. That study has since has been widely discredited, and retracted by most of its authors (see sidebar).

A quick Internet search uncovers dozens of articles, websites and discussion groups insisting the link between autism and vaccines exists. But scientific evidence establishing that link is much harder to come by.

Dr. Bryson notes the complexity of autism as a relatively new disorder (only on the books since the 1940s) may be a factor in the rise of some of the controversy. “There is so much we still don’t know about autism. Wouldn’t it be lovely if we discovered there was just one protein missing in our DNA that caused the disorder, or something simple like that? All we can say is that there is nothing in the science that has been discovered so far that suggests the answer will be that easy.”

In the meantime, she and her team continue to focus their efforts on early detection and intervention. She conducted a landmark epidemiological study of autism, the first of its kind for North America, right here in Nova Scotia in the 1980s. Since then, she and her researchers have studied 350 families for more than 10 years in a project she began at Sick Kids Hospital in Toronto.

That study has led to her current research on developing earlier autism detection and intervention for babies. She also designed and played a leadership role in implementing an early intervention treatment program for autistic children in Nova Scotia, and together with Dr. Isabel Smith, is tracking the results.

“We know that if we can get in earlier with a diagnosis, and focus on early intervention, we are better able to help the child,” she says. “The earlier the better.” Currently, her team is identifying signs of autism in children between 12 and 18 months old. So far, these signs (including delayed or lost speech, lack of social smiling, fixating on certain objects, failing to respond when name is called and unusual responses to sensations) are all behavioral. No reliable physical test is yet available.

As for the continuing debate over vaccines and autism, she says the focus needs to shift from speculation to proven fact. “There has been so much emphasis on the potential link between vaccines and autism, and not enough attention to the fact that diseases like measles can be fatal for children who are not immunized. That is a proven fact,” she says.

“It’s a lot sexier and more interesting to talk about what we think is fact, than to talk about the things we don’t know. With autism, there is still so much we just don’t know.”

   How the autism vaccine controversy began

In 1998, the prestigious medical journal Lancet published a controversial study by British gastroenterologist Dr. Andrew Wakefield and his colleagues. The study purported a link between the measles, mumps and rubella (MMR) vaccine and autism, and Dr. Wakefield urged parents not to get the combined MMR vaccine administered to their children. He suggested instead parents have vaccines administered separately for the three diseases, each spaced out by a year.

A media firestorm developed. MMR vaccination rates in Britain dropped from a 95 per cent coverage rate (which is needed to prevent the diseases from spreading) to 75 per cent, as some worried parents opted not to vaccinate their children at all.

This led to an outbreak of all three diseases in Britain that continues to this day, and has spread to other countries including Canada. (The recent mumps outbreak in this country, which was experienced here at Dalhousie, can be traced back to these developments in Britain). Sadly, Britain experienced its first deaths due to these diseases in some 15 years.

In the meantime, Dr. Wakefield’s original study—involving just 12 subjects—has since been widely discredited. Countless studies since then have failed to corroborate his claims and 10 of the original 12 authors retracted the study’s findings. Lancet retracted the study, saying that Dr. Wakefield had a “fatal” conflict of interest that was undisclosed at the time of publication; he was doing paid research for a group of parents of autistic children who were planning to sue the makers of the MMR vaccine.

Dr. Wakefield and two colleagues are currently under investigation by the British body that governs physicians for unethical behaviour. They could lose their medical licenses when hearings reconvene next month. As a result of the Wakefield scandal, MMR vaccination rates have since climbed in Britain back up to about 85 per cent. Fear and doubt over vaccines and debate about their link to autism continue to this day.


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