No link between swine flu and seasonal flu shot: public health agency

A preliminary analysis of data from hospitalized Canadian swine flu cases suggests there is no link between having a seasonal flu shot and developing a severe bout of pandemic flu, officials of the Public Health Agency of Canada said Wednesday.

They said the agency looked at data from hospitalized pandemic flu cases after learning of another, still unpublished study that seems to indicate people who got a flu shot last year had double the risk of catching swine flu compared to unvaccinated people.

The jury is still out on whether or not that study – based on data from three provinces – has found a true effect or is flawed in some way. But Dr. Frank Plummer, scientific director of the National Microbiology Laboratory in Winnipeg, called the lack of evidence of a link between seasonal flu shots and severe swine flu "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 during a media teleconference. Plummer was speaking about the analysis done by agency staff.

Dr. David Butler-Jones confirmed the Public Health Agency has received an arm's-length, international assessment of the data in the unpublished study; it had commissioned the review to help it sort through this situation, which has been dubbed "the Canadian problem" by some scientists outside this country.

He said the agency will discuss the review's conclusions with the researchers and with the provinces and territories. He said the conclusions will be made public, suggesting the timing of that would become clearer next week.

An Ontario infectious diseases expert said in his opinion, the sooner the review – and the study in question – are made public, the better.

"At this point, given . . . the whole bit about this being 'the Canadian problem' ... if you have an external review, you've got to talk about it. You have got to talk about it," said Dr. Michael Gardam, director of infectious diseases prevention and control at the Ontario Agency for Health Protection and Promotion.

"Honestly, my opinion is: It's already out there. It's out there and I would say it's important to be as open and transparent as possible."

The research in question was led by Dr. Danuta Skowronski of the British Columbia Centre for Disease Control and Dr. Gaston De Serres of Laval University. 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 pandemic flu. But the cases seen were mild disease.

Data from the United States, Australia and Britain do not show this association.

One person who had read the study said it appeared from it that getting a seasonal shot might actually have a protective effect against developing severe swine flu.

Few in the country's public health community have actually read the study, but it is nonetheless influencing public policy. The majority of provinces and territories have either scaled back or suspended plans to deliver seasonal flu vaccine in October.

Although there are a variety of approaches being taken, the most common plan is to offer seasonal shots in October only to people 65 and older – who are at low risk of catching swine flu – and residents of long-term care facilities. Pandemic vaccine will be offered when it becomes available in November and then seasonal flu vaccine will be offered to people under age 65 when the pandemic vaccine program is completed.

A variation on that theme was announced Wednesday by officials in Nunavut, who said they will not give seasonal flu vaccine this fall and will make a decision on whether to do so at all this year after the pandemic vaccination effort has wrapped up.

Dr. Isaac Sobol, the territory's chief medical officer of health, said the decision will depend on whether seasonal flu viruses are circulating, or have been apparently crowded out by the pandemic virus.

"This year is an exceptional year," Sobol said at a news conference in Iqaluit.

"H1N1 has come out of nowhere. The rules of the game have changed and we're having to be very vigilant and flexible with our decisions."