[Hardknox]

This won't be do-able this year, but it sounds interesting:

Low-dose vaccine helps block flu, study says
Younger adults seen benefiting

By Stephen Smith, Globe Staff | November 4, 2004

Scientists reported yesterday that flu vaccine given in lower doses appears to provide as much protection to younger adults as regular-strength shots and could be used to stretch limited supplies in emergencies, a finding that one of the researchers said may help ease the current vaccine shortage.

Two studies, published online yesterday by the New England Journal of Medicine, found that when substantially reduced dosages of flu vaccine were injected between layers of the skin, the immune systems of younger recipients responded just as well as when shots were given into muscle, the common site of injection. One of the teams used vaccine only one-fifth as potent as typical flu shots, raising the potential for using a single standard dose to vaccinate five healthy adults.

The diluted shots, though, did not work as well as standard vaccination in the elderly, the group at greatest peril of dying from the flu.

Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases, said that while the findings are intriguing, federal health regulators do not anticipate recommending that doctors begin diluting doses this flu season. "It's rather late in the hour to be making this kind of change," he said.

Instead, Fauci said, when scientists each year develop a new vaccine to protect against the dominant flu strain, they should routinely evaluate reduced-strength shots as well as standard vaccine.

But the lead author of one of the studies, Dr. Robert B. Belshe of St. Louis University, said that because the ongoing vaccine shortage has led to rationing of shots, doctors may in some limited circumstances want to consider dividing standard doses this year to protect more patients.

One scenario he offered involved the family members of an infant. Under restrictions imposed last week by the Massachusetts Department of Public Health, children between the ages of 6 months and 23 months remain eligible for shots, but adults who take care of those children at home and in day care centers are no longer considered among those most in need of vaccine.

"If a doctor doesn't have enough vaccine for all the family, he might consider this as an option," said Belshe, director of the Division of Infectious Diseases at St. Louis University.

In a study underwritten by the drug company GlaxoSmithKline, Belshe gave 119 adults standard flu vaccine while 119 others received injections made by Glaxo that contained vaccine 40 percent as strong as routine shots. The Glaxo vaccine is not sold in the United States.

Besides potency, the other major difference between the vaccines was the way they were administered. The shots Americans receive now are injected into muscle. But the vaccine tested by Belshe's group, as well as the other team, was injected between layers of skin in a process similar to the way tuberculosis tests are administered.

Human skin has the ability to spawn cells capable of recognizing foreign invaders and stopping them, so less vaccine injected in the skin can produce as strong an immune response as a higher dose injected in the muscle.

Blood tests performed on study participants by Belshe and his colleagues found that both vaccine methods provoked similarly strong immune responses in adults 18 to 60 years old, regardless of which kind of vaccine they got. Scientists from a Maryland biotechnology company, Iomai, report comparable findings when they gave vaccine one-fifth as potent as regular shots to healthy adults 18 to 40 years old.

But the St. Louis University team found that in patients older than 60, standard flu vaccine remained superior. Weaker shots provided only 75 percent as much protection as the standard.

Federal and state health regulators said they are eager to see results from further studies but reluctant this year to encourage doctors to begin dividing existing doses of flu vaccine. In part, that's because the reduced-strength doses that were studied are not the same vaccine available in the United States.

Health officials also expressed concerns that while most health care workers are accustomed to injecting into muscles, they usually have less experience delivering shots between layers of skin, a process known as intradermal vaccination.

"The problem is that it's a much fussier approach to giving vaccine, so you have to be trained well," said Dr. Alfred DeMaria, director of communicable disease control for Massachusetts. "If you miss with the intradermal vaccination, you have no effect against the flu."

The ability to use low doses of vaccine could prove vital if an especially pernicious strain of flu spread across the globe, said Dr. Alan C. Woodward, president of the Massachusetts Medical Society.

"If we have a pandemic and can make only a limited amount of vaccine in a short period of time," Woodward said, "we would want to stretch that as far as can be shown effective."

Stephen Smith can be reached at stsmith@globe.com.
© Copyright 2004 The New York Times Company