Seasonal Flu Shot Increases Risk of H1N1 Swine Flu?
Four Canadian studies found people who had received seasonal flu shots in the past were more likely to get H1N1 swine flu. The results are still preliminary, and has not been validated or peer reviewed.
"This is some evidence that has been floated. It hasn't been validated yet, it's very preliminary," said Dr. Don Low, microbiologist-in-chief at Mount Sinai Hospital in Toronto.
Theoretically, bacteria or virus can stimulate one's immune system to create antibodies, but at the same time facilitate the entry of another strain of virus.
This finding raises the debate between seasonal flu and swine flu, about whether or not they should delay, shorten, or cancel seasonal flu vaccination.
Across Canada, public health authorities are debating the idea of shortening, delaying or scrapping their seasonal flu vaccination campaign in favour of mass inoculation against H1N1.
The main reason is that H1N1 may be the dominant strain of influenza circulating when the fall flu season hits, meaning it could be a waste of time and resources to mount a seasonal flu vaccine campaign.
WHO said they are looking into the unpublished study. Marie-Paule Kieny said no researchers had presented similar findings, and it could be a "study bias".
"The reason why this may be different in Canada and in this particular study than in other places of the world is not yet identified. It may be a study bias, it may be that something is real," Kieny told a teleconference from the WHO headquarters.