Image: Flu vaccine
Mary Ann Chastain  /  AP file
In a study of nearly 2,000 healthy adults during a recent flu season, standard shots were twice as effective against regular winter flu as the newer nasal spray, researchers found.
updated 9/23/2009 5:09:52 PM ET 2009-09-23T21:09:52

Hate to get flu shots? A new comparison of flu vaccines gives adults a good reason to roll up their sleeves and get a jab in the arm instead of a squirt in the nose.

In a study of nearly 2,000 healthy adults during a recent flu season, standard shots were twice as effective against regular winter flu as the newer nasal spray, researchers found.

That may not be true, however, for swine flu vaccines, which may be available first in a spray. Experts say both kinds might be equally effective against the swine flu in children and adults.

Flu shots are made of killed flu viruses that are usually injected into the arm. FluMist, the only government-approved flu nasal spray, delivers a live but weakened strain to the nostrils.

FluMist is mainly targeted for use in children, and studies have suggested that it works better than shots in children. But adults are increasingly opting for the spray version as well.

The latest shot vs. spray study echoes previous research that found shots to be superior in adults.

Differences unclear
It's not clear why the spray is less effective against seasonal flu in adults, but the same may not hold true for swine flu vaccines, said Dr. Jay Butler, swine flu vaccine chief with the Centers for Disease Control and Prevention.

The swine flu virus is so novel that the immune system should still mount a strong response, he said.

Federal health officials have said they expected the first shipments of swine flu vaccines next month to be the nasal spray version. The spray is approved only for healthy people ages 2 to 49.

So should adults wait until they can get a shot that may offer more protection?

"I wouldn't recommend that," Butler said. "Even if it's less, it's not zero."

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University of Michigan epidemiologist Dr. Arnold Monto, who led the latest flu study, agreed. If there was a difference in effectiveness between the swine flu shot and spray, Monto said, it probably would not be as dramatic since the pandemic strain — 2009 H1N1 — is so new.

A look at last year's flu season
The study compared regular flu vaccines during the 2007-2008 flu season. Healthy volunteers, ages 18 to 49, were given either a flu shot made by Sanofi Pasteur of France, a dummy injection, FluMist made by Maryland-based MedImmune LLC, or a fake nasal spray.

Since the 1,952 participants were randomly divided into four groups, exposure to the flu in each group was similar, Monto said.

The flu shot was 68 percent successful at preventing the flu compared with the nasal spray, which was 36 percent effective, the researchers reported.

The 2007-2008 flu season was severe, partly because the vaccines did not work well against the circulating viruses, the CDC has said.

Results were published in Thursday's New England Journal of Medicine. The study was funded by Sanofi. Monto and several other researchers have reported receiving grants from the drugmaker.

Dr. Chris Ambrose, senior director of medical affairs at MedImmune, said the jury is still out on the issue. He cited studies that have shown FluMist to work just as well as the flu shot in adults.

MedImmune has completed studies on its new swine flu nasal spray in children and adults and have submitted results to the Food and Drug Administration. Details have not been released. Ambrose said early results indicate the new nasal spray vaccine is safe and effective.

This week, the FDA said because the swine flu shots are behaving so much like seasonal flu shots in tests, it expects the swine flu nasal spray to work the same, too.

Dr. Peter Katona of the University of California, Los Angeles, said if the current flu season worsens, people will opt for whatever swine flu vaccine is available.

"If there's very little flu activity, I wouldn't rush to get the swine flu nasal vaccine, but I would recommend that people ultimately get vaccinated," Katona said.

© 2013 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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