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, Jenny McCarthy claimed 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.

 “I’m just a mom,” she added.

Despite the lack of credible scientific evidence establishing a connection between vaccines and autism, debate rages on.

With autism rates continuing to rise (estimated at one child in 150 in the U.S.), 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?

While experts say there is no reliable way to track the impact of the controversy on North American 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.

Autism is 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,” says says Susan Bryson, the Joan and Jack Craig Chair in Autism Research at Dalhousie University in Halifax, “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, 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.

“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,” Bryson 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.”