Study finds injected flu vaccines more effective than nasal sprays

9/24/2009

WALTHAM, Mass. Injected seasonal flu vaccines proved more efficacious — in other words, they provided better protection against contracting influenza — than did seasonal vaccines delivered through the nasal cavity, according to a report published Thursday online at The New England Journal of Medicine.

Researchers carried out a randomized, double-blind, placebo-controlled trial of licensed inactivated and live attenuated influenza vaccines in healthy adults during the 2007–2008 influenza season and estimated the absolute and relative efficacies of the two vaccines.

A total of 1,952 subjects were enrolled and received study vaccines in the fall of 2007. Influenza activity occurred from January through April 2008, with the circulation of influenza types A (H3N2) (about 90%) and B (about 9%). Absolute efficacy against both types of influenza was 68% for the live attenuated vaccine.

In terms of relative efficacy, there was a 50% reduction in laboratory-confirmed influenza among subjects who received inactivated vaccine as compared with those given live attenuated vaccine.

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