The seasonal flu vaccine is not a contributor or a cause of severe disease from H1N1, evidence suggests. (CBC)

If there are lawsuits over the H1N1 vaccine, it will be the federal government, not the vaccine maker, that picks up the tab for any damages awarded by courts.

Contracts between governments and vaccine manufacturers usually include an indemnity clause that exempts companies if there are problems with a vaccine, Canada's chief public health officer, Dr. David Butler-Jones, told reporters Wednesday.

The provision does not apply, however, in the case of malpractice — if a doctor injects a vaccine the wrong way, for example.

Seasonal flu shots and H1N1 risk

Butler-Jones said there appears to be no increased risk of severe disease from the H1N1 virus among people who received seasonal flu shots.

"Those who have severe disease have the same rate of having been immunized with seasonal vaccine as the general population," Butler-Jones said. "So the seasonal vaccine is not a contributor or a cause of severe disease or illness in those people."

Still, the federal government, provinces, territories and researchers are reviewing preliminary, unpublished research that suggests people in three provinces who received seasonal flu shots may be at twice the risk of getting a case of swine flu that doesn't require hospitalization.

He hypothesized that perhaps people who got seasonal flu shots may have been more likely to go to their doctor to get tested for H1N1.

More information about an independent assessment of the research by international reviewers may be released to the public next week, Butler-Jones said.

The sooner that the review and the study are made public and can be scrutinized, the better, said an infectious diseases expert in Ontario.

"My opinion is it's already out there," said Dr. Michael Gardam, director of infectious diseases prevention and control at the Ontario Agency for Health Protection and Promotion. "It's out there, and I would say it's important to be as open and transparent as possible."

Studies in the U.S., Australia and Britain have not shown an association between the seasonal flu shot and getting swine flu.

Some provinces have delayed giving seasonal flu shots to most people, partly because of the unpublished Canadian research and partly to avoid confusion.

Pneumonia infections

In the United States, researchers at the Centers for Disease Control and Prevention reported Wednesday that many Americans who died with H1N1 also had bacterial infections.

A study of 77 patients who had the H1N1 virus showed 29 per cent also had bacterial co-infections. About half of these infections were streptococcus pneumoniae, which can be prevented with another vaccine.

For years, Canada has offered pneumonia vaccinations to people at risk from secondary pneumonia infections, such as seniors and those with weakened immune systems, Butler-Jones said.

Some Canadians on the front lines of health care have expressed concerns about taking the H1N1 vaccine until more is known about it and the adjuvant it contains.

The adjuvant is added to the vaccine to boost the immune response in people who are vaccinated. It may also provide some immunity if the virus mutates, said Butler-Jones, adding he has "no hesitancy" about the adjuvant.

Federal health officials said the risks from the vaccine are theoretical while the risk of severe disease and even death from H1N1 are too real to ignore.

"It's each individual's decision," Butler-Jones said. "But I'm not sure how I could counsel my family against getting something that would protect them and then watch one of my children die."

The H1N1 vaccine could increase side-effects such as a sore arm or fever. Clinical trials to date have not picked up anything more severe.

Also on Wednesday, health officials in Nunavut announced they will not give seasonal flu shots this fall and will decide whether to offer the shots later after the pandemic vaccination campaign has ended, depending on whether seasonal flu viruses are circulating at that time.

With files from The Canadian Press