The U.S. experienced two influenza pandemics prior to the current scare–one in 1918, and another in 1976. All three of these were of the same strain, H1N1. The avian flu that hit Asia a few years ago was of type H5N1. Influenza kills thousands yearly, mostly targeting the very young and old. This can be described as a U-shaped mortality curve. Why, then, are we concerned about this swine flu if the run-of-the-mill flu kills thousands anyway?

The mortality curve of this swine flu is shaped more like a “W”. Young adults appear to be targeted as well. Why not hammer out a swine flu vaccine and immunize everyone? Well, one is being developed, with hopes of also being incorporated in the influenza vaccine in the fall. There is also historical concern for mass vaccination.

In 1976, the death of an army soldier in Fort Dix, NJ from swine flu triggered panic. Gerald Ford issued a mass immunization program, and 40 million people were immunized by the end of the season. The problem? One in every thousand people innoculated with the swine vaccine developed Guillian-Barre Syndrome (GBS), a neuropathy that is typically defined by ascending paralysis. About thirty people died from GBS related to vaccination. There was only one recorded fatality from the 1976 swine flu. The lesson learned? While in retropect the vaccination program may have been more harmful than helpful, it’s unclear whether this overreaction actually staved off a potential epidemic.

So far, it appears that the swine flu has been less virulent than we anticipated, but we will have to see…

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