Using less vaccine in some people can still provide 'vigorous protection'
ST. LOUIS – New research demonstrates a possible way to more than double the available supply of influenza vaccine for adults between the ages of 18 and 60, according to a study led by Saint Louis University's Center for Vaccine Development and appearing this week in the New England Journal of Medicine.
When it comes to flu vaccinations, the conventional "one size fits all" approach for adults is coming under question, according to lead researcher Robert Belshe, M.D., director of the Center for Vaccine Development at Saint Louis University.
"We found that we can give lower doses of vaccine, 40 percent of the full dose, if we gave the vaccine not as a shot into the muscle, but if we gave the shot 'intradermally' between the layers of the skin," Belshe said. "This lower-dose intradermal vaccine worked well in adults 18 to 60 years of age."
Intradermal vaccination is an injection between the layers of the skin using a tiny needle, such as what is used for a tuberculosis skin test. Administration of the vaccine in this way involves injecting a small bleb of vaccine into the skin, much like a mosquito bite or allergy skin test, using a very small needle.
Belshe said the lower-dose intradermal vaccine did not, however, work as well in an older population.
A total of 238 volunteers were enrolled at Saint Louis University and the University of Rochester in the study. This included 130 people between 18-60 and 108 older than 60. Some people received a currently licensed influenza shot in the traditional way – full dose, using a shot directly into the muscle. A second group received an investigational vaccine by GlaxoSmithKline Biologicals intradermally and with a dose that was 40 percent of the standard dose.
Belshe said when compared with the full dose of vaccine given as the traditional shot, antibody responses to a lower dose vaccine given under the skin were as vigorous in younger persons but not in people older than 60 years.
"We are learning that the same size dose doesn't seem to fit all ages," Belshe said. "Younger people may need less vaccine, and older people may need more vaccine."
The nation's vaccine supply for younger healthy persons conceivably could be stretched 2.5 times using the scheme published in this study. People in this age group for whom the CDC recommends vaccinations (even with this year's shortages) include health care workers and all people who have contact with babies under 6 months.
The publication of the research was put on a fast track by the New England Journal of Medicine following this fall's serious influenza vaccine shortages.
Among the other study findings:
There was significantly less pain with intradermal administration versus the traditional "intramuscular" shot. There was more inflammation at the injection site using the intradermal approach. Belshe said this could be a good thing redness and swelling probably means that the vaccine is doing its job in producing an antibody response.
"More and larger studies are needed to confirm these options so that agencies such as the CDC can make recommendations to physicians," Belshe said.
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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