The CDC’s reports show the flu widespread across much of the U.S., with the South feeling particularly feverish and congested. Here in Washington, it’s the western half the state that’s been hardest hit.
The last two weeks of 2012, as people gathered for holiday celebrations, the number of people complaining of the flu to western Washington ER doctors soared past the annual baseline percentage for such cases. That last week of 2012, a total of 20,821 people came into the ER feeling sick from something like the flu. (A little more than 22 percent of the cases were confirmed to be influenza by lab tests.)
If you haven’t caught the flu yet, you might be weighing a family trip to get a flu shot — by the way, King County has an online flu vaccine finder. Before you go, here’s some news: According to a 2011 study of studies conducted by infectious disease experts, the flu nasal sprays (or LAIVs) “consistently show highest efficacy in young children (aged 6 months to 7 years),” at 83 percent effectiveness.
That said, the sprays are known to cause wheezing in children under two years of age — FluMist has the relevant caveats on their home page. Probably you’re wondering if the live version of the flu isn’t exactly what you’re trying to avoid. The difference is that the spray version’s virus can only live in the cooler climes of your nose. It creates an immune response, but dies before it can colonize your lungs.
Adults up to 49 years of age can get a nasal spray, too, rather than a shot, but they don’t show the same immunological response to the live attenuated vaccine (LAIV) as kids do. The trivalent inactivated vaccine (TIV) that’s in a flu shot rings in at 59 percent effectiveness in adults 18 to 64. That average is misleading, in a way, since the vaccine (in the studies used, which covered flu seasons between 2004 and 2009) ranged from 16 to 76 percent effective.
“The effectiveness of the flu vaccine depends on a number of factors, including how well matched it is to the circulating virus, and the underlying age and health of the person vaccinated,” says Dr. Jeff Duchin, chief of King County Health’s Communicable Disease Control, Epidemiology & Immunization Section. But “[i]nterestingly, the CIDRAP study did not find a good correlation between antigenic match and effectiveness. In addition, the 2009 H1N1 outbreak had a very well matched vaccine yet VE was still about 59 percent.”
The variability seen in the studies, then, is something of a mystery. While the two worst years for vaccine effectiveness were indeed years when the vaccines mix of flu strains didn’t correspond to what Nature served up, in another year where the same thing happened, the vaccine was almost 70 percent effective.
“Although not perfect,” concludes Duchin, “flu vaccine is still recognized as the single most important step that we can take to decrease the risk for influenza infection, related complications, hospitalizations, and deaths.”
