Injectable Vaccines More Effective for Adult Flu Than Nasal Sprays

Sept. 24 -- WEDNESDAY, Sept. 23 (HealthDay News) -- If you have the choice between a seasonal flu vaccine that comes in a nasal spray or an injection, go for the injection, new research shows.

In a study of adults tracked over one flu season, vaccines made from inactivated, or "killed," flu virus -- the injectable form -- provided better protection against the seasonal flu than vaccines made from live attenuated virus, the type of vaccine available in a nasal spray.

"The nasal spray vaccine is effective but isn't as effective as the injected vaccine," said lead study author Arnold S. Monto, an epidemiology professor at the University of Michigan School of Public Health. "But it's better to get some vaccine than no vaccine, so if you're averse to getting an injection, get the nasal spray."

The researchers stressed that their findings, published in the Sept. 24 issue of the New England Journal of Medicine, applied to seasonal flu vaccine efficacy in adults only. The same may not hold true for children, who may respond just as well to a nasal spray vaccine, or for the H1N1 swine flu vaccines that are on the way.

Researchers gave 1,952 adults aged 18 to 49 either an injected flu vaccine, a placebo injection, a flu vaccine nasal spray or a placebo nasal spray during the 2007-2008 flu season. That season, vaccines were well-matched to the predominant flu in circulation, according to the study.

Participants were reminded each week to come in for an exam and lab tests if they showed signs of respiratory illness. About 6.1 percent of participants, 119 in all, got the flu, mostly influenza A/H3N2.

Among those who got sick, participants who'd received the injected flu vaccine were 68 percent less likely to have the flu compared to those who'd received a placebo, according to the study. The flu virus was confirmed using lab tests.

Participants who'd received the nasal spray vaccine were 36 percent less likely to get the flu than those who'd received a placebo.