WEDNESDAY, Nov. 3, 2004 (HealthDayNews) -- Injecting flu vaccine in a different way could at least double the number of people afforded protection. But they're not the people who need it most, and the technique won't be ready to have a major impact on this flu season, two new studies say.
In both studies, the vaccine was given not as a shot into a muscle, as is now done, but intradermally, between layers of the skin. Intradermal injection is currently used in such procedures as a tuberculosis test. One study used half the normal flu vaccine dose, the other just one-fifth of that dose, and both reported satisfactory immune-system responses for people between the ages of 18 and 60.
But the intradermal delivery technique doesn't work for older people, the largest group at high risk of serious problems if they contract influenza, the researchers said.
And the technique is "from a practical standpoint not likely to have a significant impact on what happens this year," said Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases. The reason: "Partly because it is late in the game" and partly because the vaccine now is licensed only for intramuscular delivery, he said.
Both studies and an editorial co-authored by Fauci are to appear in the Nov. 25 issue of the New England Journal of Medicine. The journal released the information early because of the intense interest in flu vaccination caused by the loss of half the U.S. supply when British regulators found bacterial contamination in a production facility outside Liverpool, England.
One of the studies was done at Saint Louis University School of Medicine's Center for Vaccine Development. A group led by Dr. Robert B. Belshe, the center's director, gave intradermal injections of a dose containing 40 percent of the current recommended amount to 119 volunteers and compared the immune response to that of 119 volunteers who got an intramuscular shot of the standard dose.
The responses were essentially the same -- and satisfactory -- for persons between the ages of 18 and 60, Belshe said. But the immune response in those over 60 was not good enough, he said.
"As you get older, the immune system ages and doesn't work as well," Belshe said. "There is a loss of immunoactivity in the skin."
The other study was done by Iomai Corp., a Maryland-based biotechnology company. Researchers used an intradermal injection containing one fifth of the normal dose on 100 people ages 18 to 40. The injection caused an immune system response "that was similar to or better than elicited by intramuscular injection," the researchers reported.
"We need to confirm these results in a larger population before recommending that this strategy be used," said Dr. Gregory M. Glenn, Iomai's chief scientific officer. "But it is a very strong step in that direction, and studies done in the next six to nine months could show whether the strategy could be used if there is a vaccine shortage next year."
Iomai's business is not mass production of flu vaccine, Glenn said. The company hopes to make money by selling "immune stimulants" -- products that will enhance the response to vaccine in older people, he said.
Belshe said doctors and patients might work out ways to take advantage of the new findings.
"Individual practitioners might choose, in conversation with patients, to use the lower dose to try to immunize more patients," Belshe said. "Doctors are free to use the vaccine off-label, and this study provides some data to support that."
"Off-label" means the use of a drug or other medical product in a way not officially approved by the U.S. Food and Drug Administration. A change in the regulations for flu vaccine would require "appropriate clinical trials in a broad range of relevant populations," Fauci said in the editorial.
For more on who should get flu shots this season, visit the U.S. Centers For Disease Control and Prevention.