How effective is the nasal-spray seasonal flu vaccine?

In one large study among children aged 15-85 months, the seasonal nasal-spray flu vaccine reduced the chance of influenza illness by 92% compared with placebo.

In a study among adults, the participants were not specifically tested for influenza. However, the study found:

• 19% fewer severe febrile respiratory tract illnesses,
• 24% fewer respiratory tract illnesses with fever,
• 23-27% fewer days of illness,
• 13-28% fewer lost work days,
• 15-41% fewer health care provider visits, and
• 43-47% less use of antibiotics compared with placebo. 

A recent study suggested that seasonal flu spray vaccine may not be as effective as seasonal inactivated vaccine in adults, but more data are needed to confirm if one is better than the other. Both vaccines are expected to be effective against 2009 H1N1 flu. 

Last Reviewed: 10/18/2010

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