It's flu shot season again and the Winnipeg Regional Health Authority (WRHA) is reminding groups more vulnerable to infection to take advantage of free influenza vaccine clinics.

Between 10 to 20 per cent of Canadians catch the flu every year, and people with aboriginal ancestry are on the list of groups most at risk. They are hospitlized and die more frequently of flu infections than their non-native counterparts, Canada's National Advisory Committee of Immunization (NACI) says on its website.

"This isn't new epidemiology or even really new data," said Dr. Marcia Anderson DeCoteau with the WRHA. "This is a pattern that's been ongoing for at least a 100 years where First Nations people are at higher risk of getting the infection — influenza — and also having more severe outcomes."

Patterns of poverty, lower access to education, inadequate housing, food insecurity, all those types of things are what are common and have to do with our common history of colonization — not to genetic factors. - Dr. Marcia Anderson DeCoteau

Aboriginal populations are at increased risk for several reasons, the NACI says. Obesity and chronic health conditions such as diabetes, kidney disease, chronic lung disease and other illnesses are more frequently found among First Nations people, and they all increase the risk of flu infection, it adds.

Beyond biology

Beyond the biological risk factors, social determinants of health such as inadequate access to health care, food insecurity, unsafe drinking water, poor housing, poverty and overcrowding — all issues for First Nations communities — contribute to risk, Anderson DeCoteau says.

When swine flu (H1N1) started popping up and disproportionately hitting First Nations communities in 2009, some experts speculated that it had something to do with indigenous people being more susceptible to the virus due to low immunity. According to a national research team, however, that turned out to be more myth than medicine.

What we do have in common is the history of colonization that has led to these impacts in terms of the social determinants of health. - Dr. Marcia Anderson DeCoteau

In a 2009 study, researchers took blood samples from 138 indigenous Canadians between the ages of 20 and 59 years old before and after they were given the H1N1 vaccine. Researchers then compared immune system responses in the subjects — 95 of whom were aboriginal. Forty-two were Métis and one was of Inuit heritage.

Dr. Ethan Rubinstein at the University of Manitoba and his co-authors on the study said the results showed that, if anything, the immune systems of First Nations appeared to be better than non-native Canadians. They required only one vaccination dose as opposed to the normal two that non-indigenous people needed to become immune to H1N1.

"We can get off this bandwagon of inferior immunity and look for other causes," Rubinstein said at the time.

Social factors at play

Anderson DeCoteau says that as long as researchers have known about the global health gap between the general population and indigenous people and people of colour, people have tried to come up with biological explanations to try to explain things.

Even though the vaccine last year did not seem to be as effective as previously, overall it does help keep people out of hospitals - Dr. Marcia Anderson DeCoteau

"There's no genetic similarity between First Nations people in Canada, aboriginal Torres Strait Islander people in Australia, Maori people in New Zealand or Native Americans in the U.S. We're not genetically related at all but we all have these same patterns of higher rates of influenza, and really chronic diseases, too," she says.

"But what we do have in common ... is the history of colonization that has led to these impacts in terms of the social determinants of health. The patterns of poverty, lower access to education, inadequate housing, food insecurity, all those types of things are what are common and have to do with our common history of colonization — not to genetic factors."

Vaccination rates higher for First Nations

While First Nations remain among the most at-risk groups — pregnant women, seniors, young kids, health-care workers, people in care homes, those with a chronic illness and overweight or obese individuals all carry a higher risk, too — they're actually also getting vaccinated more often than others, at least in Manitoba.

Vaccine rates for the province in 2009 showed that First Nations were 2.8 times more likely to get immunized than non-First Nations people, Anderson DeCoteau says.

"The access to vaccination has improved greatly, so geographic access is not such an issue anymore," says Anderson DeCoteau, adding it would be reasonable to think First Nations immunization rates haven't dropped significantly since then.

"Even though the vaccine last year did not seem to be as effective as previously, overall it does help keep people out of hospitals, and so we should go ahead and get vaccinated."

The WRHA is providing free flu shots to all members of the public at 12 locations in the Winnipeg Wednesday through Saturday.