H1N1 flu virus (credit: NIAID/Flickr)

Ditching annual flu shots for a single stick that can protect year after year may be even harder to do than scientists thought—thanks to our own bamboozled immune systems.

Influenza viruses are infamous masters of mutation, changing themselves ever so slightly to dodge detection by immune cells. That viral variation drives the need for us to roll up our sleeves each fall instead of relying on our immune system’s memory of last year’s flu—or so researchers thought. A new study finds that although our immune systems naturally have the potential to detect and fight all flavors of flu virus, they get tricked into fighting only strain-specific battles. The finding, published Wednesday in Science Translational Medicine, suggests that making a universal vaccine may require wising up our immune cells as well as outsmarting the virus.

The study, from a group of researchers led by Patrick Wilson of the University of Chicago, examined the immune responses of 21 people after exposures to the 2009 H1N1 virus (swine flu). Researchers specifically looked at participants’ B cells, which make antibodies that help fend off the flu by seeking out the virus and marking it for an attack, as well as seeking out the antibodies themselves.

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