By Dan Vergano, Medical Tribune News Service
A flu vaccine administered by nasal spray was found to reduce
the severity of influenza symptoms among healthy adults,
researchers report.
Since 1997, nasal-spray inoculations against the flu have been
tested in schoolchildren, demonstrating 93-percent protection
against the disease in one study. Children typically carry flu bugs
for longer periods than adults and represent the most ubiquitous
source of new infections.
Researchers led by Dr. Kristin L. Nichols, of the Veterans
Administration Medical Center and University of Minnesota in
Minneapolis, tested the spray vaccine on 4,561 healthy adults
during the 1997-1998 flu season. Some 3,041 of study participants
were randomly selected to receive the vaccine, and 1,620 others
received a dummy, or placebo, spray. The vaccine contained live but
severely weakened strains of three types of flu virus, designed to
provoke the immune system into producing antibodies against the
infection.
People who received the vaccine contracted the flu at about the
same rate as those who received the placebo -- nearly one-sixth of
the participants -- reported Nichols' team in the July 14 edition of
the Journal of the American Medical Association. But the vaccinated
individuals also experienced an easing of their flu symptoms,
reported the researchers. Cases of severe illness dropped 19
percent and the number of days of having the flu fell an average of
23 percent.
Among people with severe cases of the flu, vaccination reduced
the number of days spent being ill by 27 percent. These reductions
occurred even though the vaccine flu strains did not match the
predominating type of flu virus affecting people that season,
according to the study.
``On just the basis of [reducing] disease severity, the vaccine
worked well,'' said epidemiologist Hunein F. Maassab, of the
University of Michigan School of Public Health in Ann Arbor, an
early developer of nasal-spray vaccines.
Maassab expressed some surprise at the ability of the
inoculation to react to a type of flu virus outside the strains
included in the vaccine. ``That's a plus for the live vaccine.''
Public health officials decide which strains of the flu virus to
include in vaccination shots months ahead of flu season, leaving
little time to grow alternate vaccine strains if they've guessed
wrong, he added.
According to the study, research conducted at the University of
Rochester in Rochester, N.Y. (currently under review for
publication in a scientific journal) found the nasal vaccine
reduced cases of flu 85 percent among volunteers deliberately
exposed to the virus.
Each year, at least 35 million Americans suffer a flu infection,
according to the National Institute of Allergy and Infectious
Diseases in Bethesda, Md. More than 20,000 people die from
influenza each year. The government estimates $4.6 billion is spent
annually on medical costs directly related to the illness.
The maker of the spray vaccine, Aviron of Mountain View, Calif.,
funded the study and reviewed its findings. Aviron plans to submit
product data under the trade name FluMist to the federal Food and
Drug Administration for marketing review later this year. Another
company, BioChem Pharma of Montreal, is also reportedly developing
a nasal-spray vaccine. Its vaccine is made up of dead samples of
various types of flu virus.
