Worries that having a seasonal flu shot increases one's chances of developing severe swine flu are beginning to appear to be unfounded.
A preliminary analysis of data from hospitalized Canadian swine flu cases suggests there is no link, say officials with the Public Health Agency of Canada.
The head of the agency, Dr. David Butler-Jones, told a media teleconference Wednesday that independent researchers were asked to look at data from severe hospitalized swinflu cases. That came after reports emerged about another unpublished study that suggests people who got a flu shot last year had double the risk of catching swine flu compared to unvaccinated people.
Butler-Jones says so far, the independent assessment that it commissioned has found no evidence of a link between seasonal flu shots and severe swine flu.
Dr. Frank Plummer, scientific director of the National Microbiology Laboratory in Winnipeg, called the news "reassuring."
"The most important question is: Is the seasonal flu vaccine associated with enhanced severity of disease? And there's no evidence whatsoever from Canadian data that there is," Plummer said, referring to the analysis done by PHAC.
Butler-Jones confirmed PHAC commissioned anindependent review to help it sort through this situation, which has been dubbed "the Canadian problem" by some outside this country.
He said the agency will discuss the review's conclusions with the researchers and with the provinces and territories. The study and the review will be made public soon, he said, suggesting the timing would become clearer next week.
The research in question was led by Dr. Danuta Skowronski of the British Columbia Centre for Disease Control, Dr. Gaston De Serres of Laval University, and Natasha Crowcroft of the Ontario Agency for Health Protection and Promotion.
Their work, which is currently being considered by a scientific journal, is reported to have found the puzzling link between getting a seasonal shot last year and contracting swine flu this year.
It was dubbed "the Canadian problem" because data from the United States, Australia and Britain did not notice such a link.
Several infectious disease experts and researchers have suggested the study work could be flawed. A commonly heard suggestion is that there was "selection bias" at work, meaning the type of people studied were not representative of the population in general and therefore the findings can't be generalized.
While few in the country's public health community have actually read the study, it has nonetheless influenced public policy. The majority of provinces and territories have either scaled back or suspended plans to deliver seasonal flu vaccine in October. Some - most notably, Ontario - cited the worries raised by the study as part of the reason they are suggesting most Canadians get the swine flu vaccine first before a seasonal flu shot.
With reports from the Canadian Press
