The nasal spray flu vaccine was not effective last year at preventing H1N1 infection in young children, according to health officials with the Centers for Disease Control and Prevention.
Researchers looked at data from three observational studies. They were surprised to find little to no protective benefits from AstraZeneca’s FluMist against the H1N1 strain of influenza in children during the 2013-2014 flu season. The formulation for the nasal spray vaccine is the same this year as it was last year, so health officials say it may, once again, not be effective against the H1N1 strain.
[callout1]Some suspect inadequate refrigeration may be to blame.[/callout1]
However, the same studies show the nasal spray vaccine did provide protection against A/H3N2 and influenza B viruses, which are expected to be more of a threat this year. The H1N1 strain is not expected to be a major player in this flu season.
This summer the CDC actually recommended the FluMist vaccine instead of the shot for children ages two to eight, because past studies showed it was more effective in that age group. The nasal spray formulation is made with a weakened, live virus versus a killed virus in the shot. Because of that, health officials believe it prompts a better immune response in children who have never had the flu.
That may still be the case for the other strains in the FluMist vaccine, but not the H1N1 strain. Researchers aren’t sure why that’s the case, but some suspect inadequate refrigeration may be to blame. Dr. Edward Belongia, a leading vaccine researcher, said certain characteristics of the H1N1 virus used in the nasal spray vaccine may affect its thermal stability, and in turn, its effectiveness.
The CDC has not changed any of its flu vaccine recommendations at this point, but the agency plans to investigate further.
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