Canadian Study Links Seasonal Flu Shot to H1N1

September, 24, 2009 – 07:35 pm Reporter, Helen Branswell, Medical – (THE CANADIAN PRESS)
A tube with a test samples is gathered for testing for H1N1 flu Thursday, Sept 17, 2009. (THE ASSOCIATED PRESS/Matt York)

A tube with a test samples is gathered for testing for H1N1 flu Thursday, Sept 17, 2009. (THE ASSOCIATED PRESS/Matt York)

TORONTO – An unpublished Canadian study that suggests seasonal flu shots raise a person’s risk of catching swine flu is raising concern abroad and triggering changes to flu vaccine program schedules at home.

The data, referred to as “the Canadian problem” by some scientists outside this country, are reported to link getting a flu shot last year with double the risk of contracting swine flu this year.

The link, if real, is to mild disease. One person who has seen the study says it seems to suggest that those who got a seasonal flu shot were less likely to develop severe disease if they became infected than those who hadn’t received the shot.

Though few people appear to have seen the data, word of the findings has spread like ripples in a pond in recent weeks. Provincial and territorial public health authorities planning two mass vaccination programs for this fall have been struggling with whether to let the unconfirmed findings influence the timing of their flu shot delivery efforts.

Earlier this week some expressed hope of a pan-Canadian approach. But that hope faded by Thursday as it became clear Canada’s various jurisdictions were headed in a variety of different directions.

Ontario announced it would vaccinate seniors against seasonal flu in October, but delay the bulk of its seasonal program until later in the winter. Saskatchewan said it may cancel its seasonal campaign altogether. And Manitoba said it is planning for the seasonal program to run as scheduled, but building in the capacity to change course if need be.

“When we look at the overall big picture, we believe that the strategy that we are offering is the safest and (most) effective strategy in terms of moving forward,” Dr. Arlene King, Ontario’s chief medical officer of health, said as she unveiled Ontario’s approach.

Her counterpart from Manitoba, Dr. Joel Kettner, said his province would prefer not to go that route.

“The start-stop, start-stop process is not my favourite option,” he said from Winnipeg. “What I say is: Keep going boldly forth, ready to stop on a dime.”

Kettner voiced what is likely a commonly held sentiment – a regret that the whole matter has come up at all.

“This is not my favourite way to do public health practice – in the middle of an evolving outbreak, to have to consider preliminary research as an influence on decision making,” he said, though he added that he appreciates that if scientists think they’ve found something of public health significance, they have a duty to air it.

“I fully understand why the authors decided to share this with some people and some people decided to share it with other people. I understand why they might have thought that was an important or good thing to do. But it does create problems.”

And not just in Canada. The work, which has been the topic of hours of teleconferences, is causing consternation internationally as well, a senior official of the World Health Organization said Thursday.

Dr. Marie-Paule Kieny, who heads the WHO’s vaccine research initiative, said there’s a keen interest, internationally, to go through the data in the study and see whether the research is correct or flawed.

“There’s really intense international discussions on that,” Kieny told The Canadian Press in an interview. “Because now that it’s out, everybody feels that we must go to the bottom of it and see what’s real there.”

She noted in a news conference that Canadian officials are putting together an expert panel to assess the data. Dr. David Butler-Jones, Canada’s chief public health officer, said the panel is being conducted at arms-length from the agency and the work is already underway.

Health Minister Leona Aglukkaq acknowledged the data are troubling.

“Of course it’s a concern,” she said in Winnipeg, where she was meeting with First Nations leaders.

“We’ll continue to look at the situation and monitor the situation. Once we have the information, we’ll share that information with Canadians.”

Drawn from a series of studies from British Columbia, Quebec and Ontario, the work is led by Dr. Danuta Skowronski of the British Columbia Centre for Disease Control and Dr. Gaston De Serres of Laval University.

They have submitted the paper to an unnamed scientific journal and are therefore constrained about what they can say about the work. Journals bar would-be authors from discussing their results before they are published.

“For me, it’s very important that we respect the peer-review process as good scientists. Because the implications … are important,” Skowronski said in an interview Wednesday.

“And if there are methodologic flaws, we need to be assured that every stone was turned over to make sure what we’re reporting is valid.”

Complicating the issue is the fact that scientists elsewhere have looked for a similar effect but have failed to see it. The U.S. Centers for Disease Control has said it finds no evidence of this and Kieny said British and Australian researchers have also drawn a blank when they searched their data.

Kieny said it is important to study the data with an open mind. “If there is something, it’s better that it comes out. I think one needs to keep open eyes and a fresh mind and look in all fairness to the results.”

Still, she, like others, struggled to come up with a reason for why getting a seasonal flu shot would elevate a person’s risk of catching swine flu, noting there is no evidence to suggest that getting the flu shot one year raises a person’s risk of catching flu the next.

“The plausibility seems sort of in question,” she said.

“It may be a study bias. It may be that something is real,” Kieny said during the news conference.

“But certainly the WHO as well as the regulators in all of these countries are looking forward to be able to see the data, to study the data and come with a better understanding of whether this has any chance of indeed putting people at risk, the fact that they have received a seasonal vaccination.”

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