Low-dose flu shots could stretch supply: study

CHICAGO (Reuters) - Five people can be protected with just one dose of seasonal flu vaccine, researchers said on Monday, but this finding is unlikely to have an effect on the expected coming battle with bird flu.

The researchers were able to stretch the supply of vaccine by administering doses one fifth the normal strength with injections under the skin instead of into muscle, the way full-strength doses are normally delivered.

"Although these results are preliminary, we found that the reduced dose administered intradermally -- under the skin -- was at least as effective in preventing flu-like illness as the standard, intramuscular dose of the vaccine," said Dr. Kathryn Kirkland of the Dartmouth-Hitchcock Medical Center in Lebanon, New Hampshire.

The findings were presented at a meeting of the Society of Healthcare Epidemiology of America.

Kirkland said in an interview that the finding could help alleviate shortages of seasonal vaccine, but could not be extrapolated to a vaccine for protecting humans from bird flu, if one is developed.

She said preliminary research has indicated that a stronger dose would be needed for bird flu than was used in the seasonal flu experiment.

Researchers fear the H5N1 strain of avian flu will mutate into a form that can pass easily among humans, setting off a pandemic that could kill millions. No vaccine can be made until the virus undergoes such a change, if it does.

Kirkland's study was prompted by the 2004 shortage of flu vaccine, when half the U.S. supply was wiped out by contamination at one of two flu vaccine manufacturers.

The study vaccinated 1,602 healthy people who received a reduced-dose vaccine, which produced similar results as the standard dose.