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June 21, 2009
Five-to-40-year-olds and Canada's aboriginal communities should be the first to get vaccinated against human swine flu, experts say as Canadian officials decide who gets priority for the flu shots.
Under Canada's official pandemic plan, the entire population would ultimately be immunized against the H1N1 swine flu.
But the vaccine will become available in batches, meaning the entire population can't be vaccinated at once. It might take four or five months to get all the vaccine we're going to get, during which time a second wave of swine flu may well be underway.
The Public Health Agency of Canada is working on a priority list, deciding where the first batches should go, and who should get the injections first. All provinces and territories would be expected to follow the national prioritization scheme.
Unlike normal seasonal flu, the H1N1 virus appears to be disproportionately infecting older children and young adults. So far the largest number of confirmed cases have occurred in people between the ages of five and 24.
"It doesn't mean they're all getting sick and need to be hospitalized, but they're getting significant illness," said Dr. Noni MacDonald, a leader in pediatric infectious diseases and a professor of pediatrics at Dalhousie University in Halifax.
British researchers reported last week that targeting children first would protect not only them, but also unvaccinated adults.
"Even if you are concerned about the elderly, who are often mentioned as another risk group, their main connection to the big pool of infection is often their grandchildren," said Dr. Thomas House of the University of Warwick.
But adults older than 64 don't appear to be at increased risk of H1N1-related complications so far in the outbreak. It's possible they have some antibodies against the virus.
As well, children "are known to be really important for transmitting flu," said Earl Brown, executive director of the Emerging Pathogens Research Centre at the University of Ottawa.
"They're important for the cycle of infection. They tend to be naive as far as not having flu antibodies in their system before. And really young kids, their immune systems aren't fully mature.
"Children tend to be hit, and they can be hit harder," Brown said. By immunizing children first, "you get to try to block spread, and protect a vulnerable group."
Gymnasiums would be used for mass school-based vaccination programs but experts say the harder to reach group will be the 18-to-30-year-olds.
"Some of them are in school, a lot of them are not," MacDonald said. "They're very much living in the moment and don't necessarily see themselves as being at risk. We need some fast thinking about how to reach those people."
She suggested booths could be set up outside bars for information and immunization.
"You've got to be creative about this and really think out of the box."
Canada's aboriginal communities also appear to be getting more serious infections. Crowded, poorly ventilated housing and poor access to high-quality running water and sanitization are some of the factors being blamed. Aboriginals also have higher rates of asthma, chronic lung disease, obesity and diabetes — the very diseases early data suggests puts people at higher risk of life-threatening complications from swine flu.
The H1N1 vaccine will be a separate vaccine from the regular, annual flu shot. People will require two jabs, and possibly three, depending on how effective the vaccine is in producing immunity. The Public Health Agency of Canada says that no decisions have yet been made about who would get priority first.
One of the challenges will be getting people to agree to the shots. There will be limited information about any vaccine's safety before immunization campaigns are rolled out across the country.
"We usually do research in healthy adults before we do it in children, because this is a new vaccine, and you want to be sure that it's safe and effective before you give it to vulnerable populations, or populations who don't have full capacity to make an informed decision about getting it or not," said Dr. Joanne Langley, of Health Canada's National Advisory Committee on Immunization.
"There are pros and cons to putting (children) first."
Babies under six months of age are not vaccinated against flu.