This is troubling news for folks with allergies and asthma, who are often counseled to get the seasonal flu shot because of their health issues: an unpublished Canadian study apparently shows that if you got last year’s flu shot, you could be more susceptible to swine flu this year.

The study was done in the provinces of British Columbia, Ontario and Quebec. While few have actually read the report, the US Centers for Disease Control is already paying attention – as are other health organizations.

The CDC has not seen greater susceptibility for contracting H1N1 if the individual had last year’s seasonal flu shot – but agrees that it’s an important issue, according to spokesperson Joe Quimby.

Unfortunately, the study will not be published any time soon: it is still being peer-reviewed by an unnamed journal. However, the explosive nature of the study’s conclusions have meant that the results been picked up by the media.

If the study is correct, the results could change the responses of health officials worldwide. Given the research which already indicates that H1N1 is more contagious than any existing seasonal flu strain, there is some question as to whether a regular flu shot is necessary. The fact that it would mean two separate injections is a concern. If there is an interaction between last year’s flu shot and H1N1, then what are the implications of getting both vaccinations just as flu season takes off?

Ontario will proceed with both seasonal flu clinics and swine flu clinics, with high risk populations targeted first. However, in Quebec, the seasonal flu program is on hold.

Karine White, speaking on behalf of the Ministry of Health and Social Services in Quebec said that many options are being reviewed, including scrapping the seasonal flu program completely for this year.

Dr Neil Rau, an infectious disease expert, wonders if having two vaccine programs will confuse people. He proposes that holding off the seasonal flu vaccination might be best. “You end up giving – especially kids – a huge number of needles”, said Rau. This also means a potentially large dose of mercury for small children, as both the seasonal flu vaccine and the H1N1 vaccine contain mercury in multi-dose vials.

As an additional concern, it’s possible that the vaccination program won’t be effective, due to the timing of the vaccine. Given that the “second wave” of H1N1 is already starting, mass vaccination in November could be too late.

Sources: CTV News; CDC