As Toronto's measles outbreak continues to grow, a new survey reveals that one in five people still put stock in the long-debunked notion that vaccines cause autism.

Two-thirds of those surveyed say unvaccinated children should be barred from child-care facilities.

On Friday, Toronto Public Health said the city now has six laboratory-confirmed cases of measles. They do not appear to be linked, which indicates the measles is "currently circulating" in Toronto, spokeswoman Lenore Bromley said in an e-mail. Two children under 2 and four adults have been infected. The latest case involves an adult born before 1970 who had been vaccinated. Although the vaccine is 95-per-cent effective, some people may not mount an immune response, and the protection can fade over time. This week, officials also confirmed that an unvaccinated woman in her 20s from the Niagara region has the measles.

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Shelley Deeks, medical director of immunization and vaccine-preventable diseases, said she would not be surprised if more cases are confirmed, but officials hope the virus can be contained, which will involve urging unprotected people to get immunized.

The new survey, conducted by Mainstreet Technologies, asked thousands of Alberta, Saskatchewan and Ontario residents about the measles vaccine, and about 20 per cent said they believe it could cause autism. An additional 20 per cent said they neither agreed nor disagreed with that statement.

"It doesn't surprise me. It more saddens me," Dr. Deeks said. "There's absolutely no evidence that vaccines are linked to autism."

Unfounded fears over the measles, mumps and rubella (MMR) vaccine arose in the late 1990s after a now-disgraced researcher published the results of a trial that purported to show a link between the shot and autism. It later emerged the researcher misrepresented or changed the medical histories of the children in the study and that the families in the trial were involved in a lawsuit against the vaccine maker. No one has been able to replicate the original findings, and the study was formally retracted.

Endemic measles was officially eliminated from Canada in the 1990s. Now, cases typically start when a Canadian is infected outside the country. The virus is highly contagious, and can easily spread to those who have not been vaccinated. Although officials say vaccination rates against the measles remain relatively high in Canada, those who remain unvaccinated can help the disease to spread, leading to outbreaks. Some object to the vaccine on religious grounds while others believe it is unsafe.

Public-health experts have long been calling for a national vaccine registry to better identify unvaccinated groups and conduct more robust disease surveillance.

Canada currently recommends that babies not receive their first dose of the MMR vaccine until they are 12 to 15 months old. Although it's possible to vaccinate children as early as six months, the protection may not be as great, so experts recommend that the child's immediate contacts be vaccinated.

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More than 100 people have been affected by measles in the U.S. in recent weeks, with most of the cases tied to an outbreak that began at Disneyland in California.

Last year, hundreds of people in B.C.'s Fraser Valley and dozens in Alberta had measles.