( r protection against type B infections ...)Flu shot effective against drifted influenza, nasal spray vaccine less so

The live attenuated vaccine marketed as FluMist was developed at the University of Michigan by Hunein "John" Massaab, professor emeritus of epidemiology. MedImmune produces it under a license with the University.

Monto's research team is conducting a randomized, double-blind, placebo-controlled three-year trial with National Institutes of Health funding in which the two vaccines are being compared head-to-head and against a placebo. Prior to the 2004-05 flu season, they vaccinated 1,247 people aged 18 to 46 in four Michigan communities.

A source of confusion about vaccine effectiveness against drifted viruses may stem from study design. Many vaccine evaluation studies rely on a clinical diagnosis of "influenza-like illness," or measures of the immune response to infection in the blood. For the present study, Monto and lead author Suzanne Ohmit, assistant research scientist in epidemiology, took throat swab specimens from participants experiencing flu symptoms and analyzed them, using virus isolation and PCR techniques, to determine if influenza virus was causing the illness.

Monto and Ohmit suspect that the adult participants in their study in 2004-05 had enough prior experience with influenza that the live attenuated virus may have failed to infect their nasal passages and initiate an immune response as it is intended to do. However, both still believe that the nasal spray is very effective in children and may be more effective than the killed vaccine in the young.

"FluMist works very well in children with naive immune systems," Ohmit said. The FDA approval of FluMist limits its use to people between age 5 and 49 years.

In another paper in the same edition of the New England Journal of Medicine, FluMist was administered to school children and the children were followed to see if they and
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Source:University of Michigan