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The makeup of influenza vaccines is adjusted annually to meet the changing antigenic characteristics of circulating influenza A and B viruses. The vaccines used for the 2004–2005 season were less closely matched than usual to circulating viruses. Two newly reported studies involving 2004–2005 vaccines provide new information on how influenza vaccines work in community and household settings.
In a randomized, double-blind trial involving 1247 healthy Michigan adults ages 18 to 46, Ohmit and colleagues compared inactivated (intramuscular) and live attenuated (intranasal) vaccines against placebo. Vaccinations were administered from October through December 2004, before circulation of antigenically drifted viruses; influenza surveillance was co…