Hundreds of Albertans are lining up to get flu shots as the number of confirmed cases of H1N1 climbs in the province, with residents saying they are getting vaccinated out of concern for little children.

The line at Calgary's mass immunization clinic at the Brentwood Village Shopping Centre had people waiting for more than 45 minutes Thursday afternoon, with many adults bringing toddlers.

There have been 965 lab-confirmed cases of influenza in Alberta as of Jan. 1, with the H1N1 strain representing 920 of those cases. The flu has hit 357 people in the Calgary zone, which extends beyond city limits, and 345 of those cases are H1N1, a strain that emerged in 2009. Influenza has sent 103 people to the hospital in the Calgary zone.

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"That is just the tip of the iceberg," Judy MacDonald, medical officer for health for Alberta Health Services' Calgary zone, told reporters at the Brentwood clinic Thursday.

"We expect that there's much more influenza circulating in our communities that has not been lab-confirmed."

Alberta is running mass immunization clinics in 13 communities across the province.

The number of clinics, however, does not mean concern has spiked among government officials. The two clinics in Calgary, for example, were always part of the province's plan, Dr. MacDonald said.

The influenza vaccine will be – and always has been – available until the end of March, she said.

Alberta's annual influenza immunization blitz started Oct. 21, and it takes about two weeks before the vaccine kicks in.

Pharmacies, which lack lines like the one snaking through the Brentwood mall, can also administer the vaccination as long as the patient is over nine years old.

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Dr. MacDonald said that while this year's running total of influenza cases is "a little bit higher" than previous years, it does not mean the flu is sweeping the province. "That number is probably influenced by all the media attention that we've been having lately and people with symptoms of influenza saying, 'Hmm, I wonder if that's what I got. I'll go see my doctor.' "

People between the ages of 20 and 65 are most susceptible to the H1N1 virus, she said. The elderly are at lower risk because they have "been around a long time" and may have been exposed to it. Children, Dr. MacDonald said, are also at lower risk.

However, an increasing numbers of adults in their child-rearing years are becoming convinced that getting a flu shot, which is free, 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 that had the highest rates of flu-shot converts.

"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.

Rich Byfield – or at least his wife, who got a flu shot in the fall – fits into that category.

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Mr. Byfield, who does not get annual flu shots, was in line at Thursday's clinic with his two girls, aged 7 and 12.

He is a flight attendant and believes exposure to thousands of customers builds up his immune system.

But he came to Calgary from his home in Cochrane, about 40 kilometres away, for the shot. "Because my wife wants me to," he said.

A small poke in the arm for him and his girls, he said, will "avoid an argument."

Dr. MacDonald said it is "speculation" that Albertans are skipping vaccinations, thus driving up the number of flu cases. Alberta had a measles outbreak in the fall.

Roughly 3,500 people with influenza die each year in Canada, Dr. MacDonald said.

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This count, however, is not perfect – some of the patients may have had existing conditions.

With a report from The Canadian Press