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What exactly is the flu shot? How does it work?
The flu shot, like all vaccines, works on the principle that if the human body is exposed to a weakened version of a virus it can develop immunity to it. The flu vaccine is an injection that contains dead antigens from three different strains of influenza (the flu) virus.
Every year the World Health Organization (WHO) chooses the strains of flu virus that it thinks will be most prevalent in the coming flu season for different regions. Based on this information, the federal government's National Advisory Committee on Immunization (NACI) recommends which strains Canadian manufacturers should use to produce vaccines.
In a two-month-long process, these strains are incubated in chicken eggs, then killed, before being packaged in vials and shipped across the country.
Within two weeks of getting a shot, your body reacts to the antigens by creating antibodies that will help you fight off illness if you're exposed to any of the flu viruses identified by the WHO.
What does it protect me from? Is it effective?
Flu viruses continually mutate and at any given time there are numerous different flu strains around the world.
The vaccine provides protection only against strains closely related to the three contained in the formulation. Even then it doesn't always work. Researchers are trying to develop a universal vaccine that would provide protection against all strains of the virus, but, even if such a thing is possible, which many doubt, it's years away from production.
"It's not a perfect vaccine," admits Mary Appleton of the Canadian Coalition for Immunization Awareness and Promotion. It's generally accepted that flu vaccines are 70 to 90 per cent effective in preventing flu symptoms in healthy adults. For the young and old, the efficacy is less predictable.
Why bother if it isn't totally effective?
Influenza is highly contagious. It travels in airborne droplets ejected in a sneeze or cough and can live outside the body for as long as 48 hours. As a result, you can pick it up by shaking hands with an infected person or even by touching something, such as a doorknob, up to two days after he or she did. (So Mom was right: Regular hand washing does reduce your chances of catching the flu.)
While there were only 5,696 confirmed influenza cases in Canada last year, the government estimates that as many as a quarter of all Canadians are infected with the virus annually and each year 4,000 to 8,000, mostly seniors, die from pneumonia and related complications.
Even when it's not lethal, the illness can make you very sick. Common symptoms include fever, headache, fatigue and a cough and can last from a couple of days to several weeks. Children (and some adults) may also experience nausea, diarrhea and vomiting. Extreme cases can require hospitalization.
Canadian public health officials consider vaccinations an important preventive measure and "the first line of defence" against mass fatalities in the event of an influenza pandemic (see "The Scoop on Avian Flu" on page 4 of this article).
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