FLU SHOTS Will new method stretch vaccine?

The way the vaccine has been given is by inoculating deep into the muscle.
ST. LOUIS POST-DISPATCH
ST. LOUIS -- A new way of giving flu shots could help stretch vaccine supplies in the future, say researchers at St. Louis University and elsewhere.
The scientists found that injecting flu vaccine intradermally -- under the skin the same way tuberculosis skin tests are administered -- instead of inoculating deep into the muscle produced a more vigorous immune system response in people ages 18 to 60.
The vaccine did not work as well in people over age 60, the St. Louis University study reported. The results could mean that healthy young people could take much lower doses of the vaccine and still be protected from the flu, while older people may require larger doses.
Results of two studies on the skin-injected flu vaccine will appear in the Nov. 25 issue of the New England Journal of Medicine. They were released Wednesday because of the health implications associated with the shortage of flu shots.
Too late for this year?
The new method is likely to be important in relieving future vaccine shortages, but probably won't help stretch this year's short supply, said Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Disease.
"Theoretically it could [ease the vaccine shortage], but practically speaking, it's probably a little late for that," Fauci said.
No one is sure if the under-the-skin injections will work as well for chronically ill people and those at most risk for complications from the flu as it did for the healthy volunteers in the studies, Fauci said.
But the technique could stretch vaccine supplies and give public health workers another tool to fight off pandemic flu, Fauci said.
The St. Louis University study was led by Dr. Robert B. Belshe, director of the Center for Vaccine Development. The study compared the traditional shots with the skin injections in two groups of people: a group of 130 people ages 18 to 60, and a second group of 108 people over age 60. Volunteers were recruited at both St. Louis University and the University of Rochester in Rochester, N.Y.
Details of study
People in the two age groups got either a full dose of the 2000-2001 strain of flu shot made by Aventis Pasteur in the muscle or an injection under the skin of an experimental vaccine produced by GlaxoSmithKline. The skin inoculations used a dosage equivalent to about 40 percent of the regular shot.
Glaxo designed and paid for the study, and Belshe and others involved with the study have served as consultants for Aventis, Glaxo and other flu-vaccine makers.
Skin contains more immune cells, called dendritic cells, than muscle does, Belshe said. Those cells show other immune cells what intruding viruses look like and help direct antibody production against the invaders.
The scientists measured antibodies against influenza viruses in the volunteers' blood before and after the inoculations. The researchers found that one size doesn't fit all when it comes to flu vaccine doses, Belshe said.
The younger group showed no difference in antibody production between the two types of immunization techniques. That could mean that vaccine supplies for young, healthy people could stretch up to 2.5 times if shots are given under the skin instead of in the muscle, Belshe said.
"This could be a very big deal if we have a chronic shortage of vaccine," he said.
Difference in older people
But the older people did not make as much antibody when the vaccine was injected under the skin. Those results could mean that aging immune systems don't respond as well to vaccines and older people and those with chronic illnesses may require higher doses of vaccine to be protected fully from flu, Belshe said.
The levels of antibody in the blood of older people may not keep them from getting sick with the flu, but probably would protect them from dying and keep them out of the hospital, he said.
Volunteers reported less pain from the shallow skin injections than with the muscle shots.
People who got the intradermal inoculation did experience more redness and swelling at the injection site than those who had shots in the muscle. But the side effect is probably a good sign, Belshe said.