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:
"More and larger studies are needed to confirm these options so that agencies such as the CDC can make recommendations to physicians," Belshe said.
Established in 1836, Saint Louis University School of Medicine has the distinction of awarding the first M.D. degree west of the Mississippi River. Saint Louis University School of Medicine is a pioneer in geriatric medicine, organ transplantation, chronic disease prevention, cardiovascular disease, neurosciences and vaccine research, among others. The School of Medicine trains physicians and biomedical scientists, conducts medical research, and provides health services on a local, national and international level.