TORONTO - The U.S. Centers for Disease Control would be eager to see final or even preliminary data from an unpublished Canadian study that appears to link getting a seasonal flu shot with catching swine flu, the agency's director said Friday.
Dr. Thomas Frieden reiterated that the CDC has looked for and failed to find a similar link in data from the U.S. as a whole and in New York City, where he was health commissioner during last spring's large swine flu outbreak.
"But nothing that we've seen suggests that that's likely to be a problem," Frieden said Friday during the CDC's weekly update for the media on the pandemic flu situation.
The unpublished Canadian study, looking at records from about 2,000 people in British Columbia, Quebec and Ontario, is the source of some consternation internationally and has led to revisions in seasonal flu vaccine delivery schedules in parts of Canada.
A group of provinces - Ontario, Saskatchewan and likely British Columbia - have decided to have a three-step vaccination program this fall, only offering seasonal vaccine to people 65 and older and long-term care facility residents in October. Following the pandemic vaccination program, which will start in November, seasonal vaccination efforts may be resumed, depending on what is learned in the interim about the study.
Frieden, who was providing an update on when pandemic vaccine will be ready in the U.S., appeared to be trying to downplay the troubling findings, which are being referred to as "the Canadian problem" by some outside this country.
"It's something that we haven't seen in any of our data, nor would there be a real explanation, technically or scientifically, of how that might happen," he said.
"But we take every concern seriously and we will absolutely look at any data that is made available to us. But what I can say again is that we've looked very carefully at our own data in this country. I've looked at data from New York City. Australian data have been analyzed very carefully. And none of it suggests any problem from getting the seasonal flu (shot) in terms of H1N1."
A spokesperson for the CDC said the agency is in active discussions with Canadian colleagues and other vaccine experts about the data.
Meanwhile, the issue has caught the attention of the CDC's Team B, a group of outside experts that the CDC has set up to critique and offer advice on the agency's pandemic response.
Dr. David Sencer, who headed the CDC during the 1976 swine flu crisis, said via email that "it is likely that Team B will discuss" the data and the dilemma they pose.
Other members of Team B are antiviral expert Dr. Frederick Hayden of the University of Virginia, Dr. Marc Lipsitch, an infectious diseases modelling expert from Harvard University, and Dr. Harvey Fineberg, head of the U.S. Institute of Medicine and author of the report on the 1976 swine flu affair.
In that incident, fears of a swine flu pandemic led to the vaccination of more than 40 million Americans. The virus never took off, but about 500 cases of Guillain-Barre syndrome that were thought to be linked to the vaccine were reported, and 25 people died from the paralytic condition.
In Canada, Chief Public Health Officer Dr. David Butler-Jones concurred that "it would be very unusual" for a vaccine to increase the risk of catching another strain of the same virus type.
"It's an unusual finding," he said Friday during a media conference in Ottawa.
"It's not been seen before with ... seasonal influenza vaccines. It's been studied in several other countries quite extensively. They have not found the same relationship. So we're not sure exactly why we've seen that or the suggestion of that. I think a lot more work needs to be done."
That work includes an independent arms-length assessment of the data, which is underway.
