Canada will ship out more influenza vaccine this season than it has since the H1N1 pandemic swept the country four years ago, with nearly every province and territory placing late-season orders to satisfy a surprising surge in demand for the flu shot.
The 2013-2014 season marks the first time since the pandemic that Canada has been forced to track down extra vaccine, above and beyond a five-per-cent cushion built into the country's contracts with vaccine makers, according to the Public Health Agency of Canada.
"With this season – for whatever reason and we can only theorize – but there has been a lot more uptake, a lot more demand by Canadians," said Dr. Gregory Taylor, Canada's deputy chief public health officer.
Only Nova Scotia and Nunavut declined to snap up more vaccine when Ottawa secured more than 400,000 extra doses earlier this month, according to an informal survey by The Globe and Mail.
Newfoundland and Labrador increased its vaccine supply by the largest amount – 62 per cent – by requesting an extra 80,000 doses on top of the 130,000 it ordered at the start of the influenza season. Saskatchewan and Manitoba were not far behind, increasing their stockpiles by 53 per cent and 29 per cent, respectively.
Canada had already ordered approximately 10.8 million doses at the start of the season, about the same size of the order it placed at the beginning of the 2010-2011 season and more than any year since, according to the Public Health Agency of Canada (PHAC).
The demand is particularly puzzling because, as public health officials have been stressing, this has been a typical flu season.
That raises a question that is as difficult to answer as the flu virus is to predict: What makes Canadians clamour for flu shots one year and eschew them the next?
"It's really quite unusual," Dr. Michael Gardam, one of the country's top flu specialists, said of the late-season purchases. "It's been a very average season. "
The prevalence of H1N1 this year could explain the surge, experts say.
More than 90 per cent of the flu cases detected this year have been H1N1, now considered a regular seasonal flu virus.
Some provinces have been hit harder than others: Saskatchewan, for instance, announced Friday that 16 people in the province had died of the H1N1 strain of the flu, one more than in the pandemic season of 2009-2010.
"The word H1N1 is scarier than regular flu and that drives demand," said Dr. Allison McGeer, director of infection control at Toronto's Mount Sinai hospital.
H1N1 also tends to strike people between the ages of 20 and 64. Last year, H3N2 dominated and hit more seniors. Both strains are included in this year's flu vaccine, along with a type of influenza B.
Media reports of adults in this younger age group contracting the flu, falling seriously ill and dying, prompted a stampede to flu clinics, particularly in the western provinces in the last week of December and first week of January.
"It was the spike after Christmas in H1N1, the shift in morbidity and mortality to a younger age group and the media attention that that garnered," said Dr. Perry Kendall, the provincial health officer for British Columbia.
Still, January and February are not the best time to get the flu shot. Full protection does not kick in until two weeks after the shot is administered. Those who receive the vaccine today would have gone unshielded through much of the flu season.
"Waiting until that moment to get your flu shot, it's not entirely worthless, but frankly there's a reasonable chance it's not going to help you much," said Dr. Gardam, who is the director of infection prevention and control at Toronto's University Health Network. "The analogy I give is, you've never bought fire insurance, now your drapes are on fire and you're frantically calling State Farm. You're kind of too late."