Friday, January 18, 2013

Does the Flu Vaccine Work? What 62% "Effective" Really Means

JAMA has posted today a Viewpoint titled “Influenza Prevention Update: Examining Common Arguments Against Influenza Vaccination.”

In this Viewpoint, the authors (from the Vanderbilt University School of Medicine) provide perspective to some of the reasons why people refuse the flu vaccination, including:
  • The vaccine does not work
  • The vaccine causes the flu
  • I have an allergy to eggs
  • I cannot get the vaccine because I am pregnant or have an underlying medical condition or because I live with an immunocompromised person.
  • I never get the flu/I am healthy 
I was disappointed when Dr. LaPook on a recent CBS Evening News program said that this year's Flu vaccine was 62% effective in preventing the flu. First of all, I would have liked it to be 100% effective in preventing the flu. And I'm pretty sure LaPook specifically said "preventing" without qualifying what "preventing" actually means. Now I learn from the JAMA viewpoint cited above that there is a qualifier:
The Centers for Disease Control and Prevention's midyear assessment of this season's influenza vaccine's effectiveness is 62% (95% CI, 51%-71%) for the prevention of medically attended acute respiratory illness [my emphasis].
The authors note "A prevention measure that reduced the risk of a serious outcome by 60% in most instances would be a noted achievement."

Back on January 11, Vanderbilt University's Dr. William Schaffner (not an author of the Viewpoint cited above) was interviewed on "CBS This Morning" (listen here) where he "anticipated" that the vaccine is "able to prevent 60 to 70 percent of all infection." He, like Dr, LaPook, did not mention prevention in terms of preventing a "serious outcome" (i.e., medically attended acute respiratory illness).

I've taken the vaccine. So I guess I can still get the Flu, but not serious enough that I will end up in the emergency room -- at least a 60% chance that I won't end up there! I think I'm feeling slightly sick. Can it be the flu?

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