By Helen Branswell, Medical Reporter, The Canadian Press

TORONTO - Unpublished Canadian data are raising concerns about whetherit's a good idea to get a seasonal flu shot this fall and fuelling adrive by some public health officials in Canada to delay, reduce orscrap altogether campaigns to vaccinate against seasonal flu this year.

Drawn from a series of studies from British Columbia, Quebec andOntario, the data appear to suggest that people who got a seasonal flushot last year are about twice as likely to catch swine flu as peoplewho didn't.

A scientific paper has been submitted to a journal and the leadauthors - Dr. Danuta Skowronski of the British Columbia Centre forDisease Control and Dr. Gaston De Serres of Laval University - areconsequently constrained about what they can say about the work.Journals bar would-be authors from discussing their results before theyare published.

Skowronski, who initially declined to speak after news of thefindings leaked to the media, said it's important that the work getsthe expert scrutiny the journal peer-review system provides.

"Good scientists know that methods can influence results," she said Wednesday night from Vancouver.

"For me, it's very important that we respect the peer-review processas good scientists. Because the implications ... are important. And ifthere are methodologic flaws, we need to be assured that every stonewas turned over to make sure what we're reporting is valid."

"Epidemiologists are taught there a limited number of explanationsfor results," she continued. "Either they're real, they're due tochance or they're due to bias or to confounding. And so it's going tohave to be in one of those categories and that's true of any studyconducted anywhere."

While few people appear to have actually seen or read the study, thepuzzling findings have been a poorly kept secret and many in the publichealth community in Canada have heard about them.

The findings are causing consternation abroad as well, withofficials at public health agencies and even at the World HealthOrganization worried the alleged link will deter people from gettingvaccinated in a fall when many are being urged to get both seasonal andpandemic flu shots.

The Public Health Agency of Canada was informed of the findings sometime ago and has been seeking help here and internationally to try tofigure out if the effect is real or if the studies are flawed.

"An arms-length review of the various methods is currently underwayto assess the validity of the studies relative to that observation,"Dr. David Butler-Jones, Canada's chief public health officer, said viaemail.

"We are also examining other data that will help to understand whatif any association there is. We look forward to the results of thereview and other data to inform our recommendations as we go forward."

The U.S. Centers for Disease Control also knows of the work. It saidit has looked for similar evidence in the United States but sees none.

"It is difficult to speak about a study that has yet to bepublished, however, as this is an important issue involving the subjectof seasonal influenza and the fast moving global pandemic of 2009 H1N1influenza it is important to note the scientists at the Centers forDisease Control and Prevention have not seen this effect in systems wehave reviewed in the United States," spokesperson Joe Quimby said byemail.

A number of influenza and infectious diseases experts know of butare unwilling to speak publicly about the paper. But several were quickto note that British and Australian researchers haven't seen thephenomenon either. The lack of corroboration in other jurisdictions is"a red flag," said one expert, who believes the findings will be shownto be due to a study flaws.

Another flu expert who was willing to speak on the record said they do not make sense to him either.

"I cannot think of a good reason why this is biologically likely,especially since we have sufficient evidence now that ... there ispriming in the population by the way the vaccine is working," said Dr.Arnold Monto, of the University of Michigan.

He was referring to the fact that studies of swine flu vaccine showa single dose induces a strong and likely protective response in teensand adults. That suggests humankind's long exposure to seasonal H1N1viruses has "primed" or awakened our immune systems to recognize thenew virus and fight it off.

Dr. Donald Low, chief microbiologist at Toronto's Mount SinaiHospital, was reserving judgment on the findings. But he said this kindof effect of previous exposure raising the risk of future illness isseen in some diseases, like dengue fever.

"We don't see that in flu," Monto countered.

Low said it is important to get to the bottom of the issue, but inthe meantime, delaying the use of seasonal flu vaccine makes sense forlogistical reasons. Swine flu activity is on the upswing in the U.S.and in parts of British Columbia, and focusing on speeding delivery ofthat vaccine makes more sense now, he said.

"If we're going to try to protect people, this is the virus weshould be trying to protect them against," Low said, suggestingdecisions on whether to try to vaccinate against seasonal flu can bedone later in the season.

He admitted the controversy could undermine the public's willingness to be vaccinated against influenza.

"This is obviously difficult for public to be able to digest this,"he said. "There's a crying need here for a prospective randomizedcontrolled study."

That type of study - which is not the kind on which the findings arebased - is considered the gold standard of medical evidence. They arealso costly and Skowronski said it wouldn't be feasible to mount one intime to help public health officials faced with the current dilemma ofwhether to push seasonal flu vaccine this year or not.

"If it was possible, we would have attempted it," she said.

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