The flu vaccine is new every year. The influenza virus evolves quickly, and the vaccine has to change every year to keep up.
This year’s flu shot is getting some attention in the news lately. It seems like the flu shot did well protecting people for the first part of the flu season, but now cases of influenza are on the rise. Why? Because the strains that are very active this year aren’t strains that were covered in the 2008 flu shot. The U.S. Centers for Disease Control say that only about forty percent of the people who got vaccinated are escaping the flu this year.
Not very good odds for this year. That’s why the U.S. Food and Drug Administration has asked experts to work on the 2009 vaccine — predicting what flu strains will be the worst next year. The early predictions give manufacturers time to prepare more than one hundred million doses of the flu shot before next fall.
The World Health Organization also makes suggestions for the flu vaccine recipe. For 2008-2009, the WHO suggests three strains of the flu that weren’t in this year’s shot: Brisbane/10, another Type A strain called Brisbane/59, and a Type B strain that evolved in Florida. The U.S. usually follows the suggestions from the World Health Organization.
It’s important to point out that this is a rare miss for the flu vaccine. In sixteen of the last nineteen years, the flu vaccine has been well matched to the active strains. The last “miss” was 2003-2004, when a strain of the flu known as Fujian flu evolved in Asia. In that case, the vaccine was successful about fifty percent of the time.
This flu season’s main culprit is a strain of Type A flu (the harsher version of the virus) called Brisbane/10 — named for its Australian origins. The 2007-2008 flu vaccine protects against two strains of Type A flu and one strain of Type B flu, but Brisbane/10 and other mutated versions are different enough from the strains in the vaccine that they are causing trouble.