TORONTO -- Increasing numbers of adults in their child-rearing years are becoming convinced that getting a flu shot for themselves and their children is a good idea, a new poll suggests.

The Harris-Decima poll, done for The Canadian Press, found that those aged 18 to 34 and those with children in their households were the two demographics which had the highest rates of flu-shot converts than any other.

"What appears to be occurring is that over the years younger Canadians and parents are particularly becoming more convinced that they will do it (get a flu shot) in the coming year if they haven't done it very often in the past five," said Doug Anderson, senior vice president for public affairs for the polling firm.

With this year's flu season shaping up to be an H1N1 year, that's a good thing.

Newly released data from researchers at the British Columbia Centre for Disease Control suggests children under five are the most vulnerable segment of the population when it comes to this family of flu viruses.

In a submission to the online disease monitoring system ProMed, the BCCDC's flu expert Dr. Danuta Skowronski said she and colleagues looked for antibodies to H1N1 viruses in blood samples from people in a range of ages.

Less than 20 per cent of children under age five have antibodies to H1N1 viruses. That's not really a surprise; they would have been born after the 2009 pandemic which brought the new H1N1 virus into the mix of flu viruses that circulate during the Northern Hemisphere winter.

Adults aged 20 to 39 and 40 to 69 are also less likely to have antibodies that protect against H1N1, with 45 to 50 per cent and 35 to 40 per cent respectively showing antibody protection.

School-aged children and those 70 and older are less vulnerable to H1N1 viruses than other demographics, the work found. The attack rate among young children was the highest during the H1N1 pandemic, explaining the high degree of protection now within that group. And exposure to related viruses decades ago appears to have given many seniors enduring protection against this virus family.

The Harris-Decima poll reports that about 41 per cent of Canadians say they got a flu shot last year and 44 per cent have either had a shot already (33 per cent) or intend to get one this year.

Those figures may actually be over-estimates. Firm real-time figures on how many Canadians get flu shots aren't available -- jurisdictions don't keep an actual count. But estimates calculated based on Statistics Canada's Canadian Community Health Survey -- which surveys about 65,000 Canadians on health behaviours every year -- suggest that over the past five years or so, between one-quarter and one-third of Canadians have been vaccinated each year.

Anderson said he would not be surprised if the 41 per cent number was high. "I fully expect that what happens in a survey like this is people tend to over-report a socially desirable behaviour."

The poll suggested the percentage of Canadians who have been vaccinated against flu has been relatively static over the past few years. But Anderson said the firm wanted to see if the same people were getting shots every year, so they asked respondents whether they had had a flu shot at least once over the past five years.

Mining the poll's data suggests Canadians can be divided into four groups on the question of flu vaccine, Anderson said. About 27 per cent of people get a shot every year; Harris-Decima calls them "dedicated" flu shot recipients.

At the other end of the spectrum, 39 per cent fall into the "never convinced" category. They haven't had a flu shot over the past five years and won't get one this year.

In between, there are the people who fall into the "now convinced" (18 per cent) and the "eroding" (16 per cent) categories. The former are people who appear to have been won over on the value of influenza vaccine while the latter have been vaccinated in the past but don't intend to get a shot this year.

Parents living with their children and young adults (aged 18 to 34) have the biggest proportion of "now convinced" of any age group.

Skowronski said it is likely that awareness is higher these days among parents of the advisability of getting children vaccinated against flu. A few years ago the expert panel that advises on vaccine use in Canada, the National Advisory Committee on Immunization, added pre-school children and the people who live with them to its list of people who should be vaccinated against flu.

That would mean that doctors and nurses who see young children would likely raise the issue with parents, Skowronski said. As well, in the wake of the 2009 pandemic, most provinces and territories now offer free flu shots to all comers, which may have increased willingness to get children vaccinated.

Still, when people with children under the age of 18 were asked by the pollster if children in their households would be vaccinated against flu this year, only 39 per cent said yes.

Dr. Jeff Kwong is a Toronto family physician and scientist with the Institute for Clinical Evaluative Sciences and Public Health Ontario. Kwong, who has done extensive study into the issue of influenza vaccination uptake, finds the continued resistance to flu vaccine puzzling.

"There's a big misperception out there that influenza is always a benign illness. In most cases, it is benign. But it's a bit of Russian roulette: Who knows when it's going to be severe?" Kwong noted.

"People won't hesitate to get meningococcal vaccine when meningococcal disease is extremely rare. You're much more likely to have serious complications of influenza than you are to have meningococcal meningitis. People won't hesitate to get (their child) a meningococcal vaccine but they think 'Oh, influenza's not a big deal. I don't need that vaccine."'