The Centers of Disease Control (CDC) put out a health advisory to physicians last week in regards to this year's influenza (flu) vaccine. The advisory stated that the vaccine this year may be less effective than usual because of antigenetically different or "drifter" strains that have surfaced. What does this mean? A quick run down on the influenza virus and vaccines in general will make this clear.
The influenza virus has many strains. These strains are structurally different just slightly, but enough to have their own identity. It's almost like hair color. It's still hair, but it can be black, red, brown, or even blue in some teenagers. In the same way, the influenza virus has differences. Every year, the flu vaccine is developed in order to provide immunity against the most common strain for that year. However, this is somewhat of a guessing game. The flu vaccine is actually developed earlier in the year with only a very small sample size of influenza strains that have been captured. For that reason, a flu vaccine does not cover every single strain of the flu, only the one(s) that we predict will be the most common this year.
That takes us back to this year's flu vaccine. This year it was predicted that a specific type of H3N2 strain of the flu would be the most common. So they developed the vaccine that was appropriate. Now they have discovered that as many as 50% of the strains in the population may be different than the strain that the flu vaccine covers. The strain is still H3N2, but it's like instead of having brown hair, you've thrown in red highlights. This subtle change is enough that the body will not be able to form antibodies to it and it can still lead to an infection.
The flu vaccine is never perfect because there are so many different strains and it is almost impossible to protect all of them. Even if the flu vaccine covers 100% of the most common strain for the year, you can still get the flu from uncommon strains. So the question is, do we vaccinate? The recommendation from the CDC is still to receive the flu vaccine because protecting against 50% of the strains is better than not protecting against any. What we will see though is that the flu season this year may be pretty bad in most parts of the country and more people will need anti-viral medications at the first onset of the flu. So remember to get your flu shot this year, just be aware that a brunette with red highlights may still spoil the party.
Have you or will you get a flu shot this year?
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