We caught up with Dr. Curtis Boyington, a medical doctor in Alberta specializing in infectious diseases at the Grey Nuns Community Hospital, to help us gain a better understanding of the influenza vaccine. Here's what you need to know about the flu shot.
Each year the flu vaccine is designed to cover the expected strains of influenza for the season. Two strains of influenza A and one strain of influenza B are included in the vaccine annually. The choice of the three vaccine components is based on what strains are circulating during the Southern Hemisphere winter.
After vaccination, our immune systems produce antibodies that
will protect us from the strains in the vaccine. Should we be exposed to the
live virus versions of the strains we have been vaccinated against, we should
be well protected against them.
The vaccine contained a strain of H3N2, which was the predominant influenza A strain circulating last season. However, there was a mutation (antigenic drift) in this strain, which rendered the H3N2 component of the vaccine less effective. Essentially, the antibodies generated by the vaccine were less able to bind to the antigenic sites on the virus. For this strain, less than a quarter of people vaccinated were protected against the virus, according to Centers for Disease Control (CDC) data.
No. Even with the reduced effectiveness of the vaccine, mortality and hospitalization rates decreased for those who did get some protection from the H3N2 strain. As well, the non-mutated strain of H3N2 was also circulating (though in lesser numbers than the mutated strain), and the vaccine worked against this strain. Most important, the other influenza A strain and the influenza B strain included in the vaccine were effective.
Yes. We expect the influenza vaccine to be much more effective this year. The mutated strain of H3N2 has been included in this year’s vaccine. Through immunization we are protecting ourselves, our co-workers, our patients and our families from potentially serious and preventable infections. Annual influenza vaccination, accompanied by hand washing, is the most effective measure to decrease spread of infection and decrease illness and death associated with influenza infection. With this in mind, Alberta introduced an annual universal influenza immunization program in 2009.
As you know, influenza is a respiratory infection predominantly caused by strains of the influenza A and B viruses. Influenza strikes mainly in the late fall and winter months. Rates of serious illness and death are highest in the very young (less than two years old), those over 65 years old, and people with underlying medical conditions. People with compromised immune systems are particularly vulnerable. However, the entire population is at risk of influenza, and as much as 10 to 20 per cent of the population are infected with influenza each year. About 3,500 deaths per year in Canada are attributed to influenza.
Now. It takes 14 days for the vaccine to achieve a protective immune response in your body. The sooner you get it, the sooner you will be protected.
Though the main strain of
influenza circulating last year developed a mutation that rendered one
component of the vaccine less effective, the vaccine still protected against
two other circulating strains of influenza. We expect a much more effective
vaccine this year, particularly against the H3N2 strain. The vaccine combined
with hand washing is the safest and most effective way to protect patients,
families and ourselves.
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