The recent studies determining this appeared in the latest issue of Vaccine. One study compared the 2010 CSL vaccine with versions from earlier seasons and with other trivalent inactivated influenza vaccines (TIVs). Another study looked specifically at what role viral RNA and lipids in the vaccine might have played in the adverse events.
Researchers in the first study reported that the combination of the influenza B component with the 2009 H1N1 virus component in the 2010 vaccine resulted in heightened cytokine and immune response, which maybe have been associated with the febrile seizures.
Higher-than-expected rates of fever and convulsions in children younger than five after receiving Fluvax or another flu vaccination during the Southern Hemisphere's 2010 flu season, prompted Australia and New Zealand to recommend that flu vaccination be suspended. CSL removed it from the market and vaccine advisers in the Unites States recommended that it not be used in children under age five during the Northern Hemisphere's 2010-11 flu season.
Pandemrix, a flu vaccine for influenza pandemics like the H1N1 2009 flu pandemic or Swine Flu, was developed by GlaxoSmithKline and patented in September 2006. Health reports in 2010 linked the vaccine to narcolepsy in some patients and studies have shown that the vaccine increased the risk of the sleep disorder tenfold (as indicated by the British Medical Journal).