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Back to Infectious Disease Articles
Friday 26th May, 2006
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High-dose influenza vaccines may
increase elderly patients' immune response without
significant adverse effects.
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There may be a simple way to provide elderly Americans with
extra protection against the annual flu virus: give them a
higher dose of seasonal flu vaccine.
This idea is suggested by the results of a newly reported
clinical trial supported by the National Institute of Allergy
and Infectious Diseases (NIAID), a component of the National
Institutes of Health (NIH).
The trial, described in the latest issue of the Archives of
Internal Medicine, was conducted by a team of researchers from
Baylor College of Medicine in Houston, TX, and sanofi pasteur,
the vaccines business of the sanofi-aventis Group in Paris. Led
by Dr. Wendy Keitel, M.D., the team conducted the trial at the
Baylor Vaccine and Treatment Evaluation Unit, which is one of a
network of NIAID-supported sites at university research
hospitals across the United States that conduct Phase I and II
clinical trials to test and evaluate candidate vaccines for
infectious diseases.
NIH Director Elias A. Zerhouni, M.D., notes, "The study
results reported by Dr. Keitel and her colleagues are important
because they suggest that a higher dose of seasonal influenza
vaccine can safely and significantly increase the immune
responses of older people."
"Elderly Americans are among the most vulnerable to serious
complications of influenza because they generally have more
underlying diseases and weaker immune systems than younger
people," says NIAID Director Anthony S. Fauci, M.D. "These
findings are an important first step in developing new
strategies to better protect the elderly against
influenza-associated hospitalizations and mortality."
"If you look at people who are dying and going into the
hospital during an outbreak of seasonal influenza," says Dr.
Keitel, "the majority of those people are older individuals."
Influenza accounts for some 36,000 deaths and more than
200,000 hospitalizations every year in the United States. It is
among America's most lethal killers simply because the virus
infects so many people--some 5 to 20 percent of the U.S.
population every year.
In other influenza vaccine studies, higher antibody levels
resulted in better protection against infection. Conversely,
decreased antibody production in the elderly can leave them more
susceptible to infection and the severe complications of
influenza. Helping elderly people increase antibody production
should help them fight off influenza infections, and this is
exactly what Dr. Keitel and her colleagues set out to test when
they began the clinical trial. They hypothesized that elderly
people could be given higher doses of vaccine safely and that
these higher doses would increase the antibody response and
confer increased protection without increasing side effects.
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In the study, the investigators randomly assigned 202 adults 65
years of age or older into four equal-sized groups: those
receiving the normal dose of vaccine (15 micrograms); twice the
normal dose (30 micrograms); four times the normal dose (60
micrograms); or a placebo. The average age of the volunteers was
72.4 years. All study participants were followed for a month
post-vaccination to look for any vaccine-related side effects
and to collect blood to evaluate antibody responses.
Dr. Keitel and her colleagues found that participants in the
high-dose group (60 micrograms) had 44 to 79 percent higher
levels of antibody than did those who received the normal dose
of vaccine. Higher doses also increased the number of elderly
volunteers achieving levels of antibody that have been
associated with protection against influenza. Moreover, the
vaccine was well-tolerated at all dosage levels. Although the
higher doses of vaccine caused more mild side effects at the
injection site, there were no significant differences in
systemic symptoms such as fever or body aches among the groups.
The successful achievement of higher levels of antibodies in
this study suggests that larger doses of vaccine may be a safe
and viable way of enhancing protection against influenza among
elderly persons. These promising results provide a basis for
further evaluation of enhanced potency vaccines in the elderly,
says Dr. Keitel.
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