Booster Shots

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Vaccine problems for seasonal flu

July 25, 2009 |  8:42 am

As if the world didn't have enough problems in developing a vaccine against the new H1N1 influenza virus, commonly known as swine flu, reports from the Southern Hemisphere suggest that there may be problems with the seasonal flu vaccine that has been produced for this winter's flu season.

The Canadian Press reports that some laboratory tests indicate that there is a new strain of the H3N2 flu virus -- one of three strains included in the flu vaccine -- that is different from the A/Brisbane/10 strain of H3N2 that was selected for the vaccine. If that is the case, then the vaccine will provide less protection than health authorities had hoped.

The new strain has shown up only in a few laboratory tests, but that may be because labs have been looking so hard at swine flu isolates that they have had little time to study seasonal flu, which has been perceived as less threatening.

Health authorities will be keeping an eye on nursing homes this fall because the H3N2 strains prey particularly hard on the elderly. That could be doubly troublesome because the elderly seem to have at least some immunity to swine flu because of past exposure to related strains. That immunity would leave a niche for the new H3N2 to attack.

-- Thomas H. Maugh II