With the annual flu season just getting underway in Canada, some experts are worried that many Canadians, perhaps jaded by last year's "swine flu" pandemic, are not getting their flu shots.

While it appears that Europe is still seeing a lot of last year's H1NI flu strain circulating, here in Canada, H1N1 is almost non-existent. The predominant strain here is one called H3N2.

Early signs from the Public Health Agency of Canada suggest that most parts of the country are seeing a normal flu pattern so far, with a typical number of illnesses and hospitalizations. However, a spike in flu cases has been reported in localized parts of Manitoba, British Columbia, Alberta, Quebec and Nova Scotia, and along the Windsor to Montreal corridor in Ontario.

In Toronto, officials have confirmed 515 cases of flu so far this year, compared to an average of about 81 cases by this point in the season over the last few years.

Even still, that differs from this time last year, when there was already a huge spike in the number of Canadians testing positive for flu, as H1N1 hit its peak in the fall.

But as the flu season progresses, some are worried that more Canadians will fall ill if vaccination rates stay low.

Dr. Allison McGeer, the head of infection control at Toronto's Mount Sinai Hospital, says she thinks fewer Canadians are choosing to get the annual flu vaccine this year -- and that could cause problems as the flu season goes on.

"We don't know for sure yet, we haven't seen the data, but the evidence is that not as many people got their flu shot this year as usually get it," McGeer told CTV News.

In Toronto, public health officials say 20 per cent fewer people have received the annual flu shot at its clinics compared to 2008 and 2009. Dr. Irene Armstrong, the city's associate medical officer of health, says of the 515 confirmed cases of flu in the city, 300 are the H3N2 strain. So far, five deaths in Toronto have been linked to the flu.

With less vaccine protecting people, that means the possibility of more flu cases -- and the possibility of more deaths.

"Seasonal flu does a lot of damage, causes a lot of deaths every year and the more of us who get our flu shots, the better protected we are," McGeer says.

Armstrong said it is unclear why so many people have neglected to get the shot, but officials speculate "it has something to do with last year's pandemic.

"There were a lot of campaigns and media attention encouraging people to get vaccinated, but it turned out to be a mild flu season and a mild pandemic, so perhaps it has fallen off people's radar," Armstrong told CTV News.

Dr. Scott Halperin of the Canadian Centre for Vaccinology, said experts can't predict how severe a flu season will be or when an outbreak will grow to pandemic proportions.

So Canadians who hope to wait out the winter to see how severe the flu season turns out to be shouldn't wait.

"The best prevention or best way of avoiding severe disease is through the vaccine," Halperin told CTV News Channel Tuesday evening. "And if one waits to see how severe the pandemic really is, it may be too late."

The good news is that H3N2, the strain causing the majority of illness across Canada, is part of this year's flu vaccine.

The bad news is that H3N2 has already led to the hospitalizations of hundreds of Canadians, including the frail and elderly, a demographic more susceptible to the strain.

Dr. Ken Scott of the Public Health Agency of Canada chalks up this year's slide in vaccinations to "human nature," an expected drop-off given that 45 per cent of Canadians got the shot last year.

But still, Scott told CTV News, H3N2 "causes a lot of illness and death, so we anticipate that we will see some problems, and vaccine is the cornerstone of protection."

With a report from CTV medical specialist Avis Favaro and CTV Toronto's Pauline Chan