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NIH Research Matters

May 26, 2006

Higher Dose of Seasonal Flu Vaccine Provides Extra Protection

A new clinical trial suggests there may be a simple way to provide elderly Americans with extra protection against the seasonal flu: give them a higher dose of vaccine.

Influenza illustration

Seasonal influenza, or seasonal flu, accounts for some 36,000 deaths and more than 200,000 hospitalizations every year in the United States. It's among America's most lethal killers because the virus infects so many people — 5 to 20% of the population every year.

Previous seasonal influenza vaccine studies have found that the higher the levels of the virus-fighting molecules called antibodies a person produces, the better they're protected against infection. A team of researchers from the Baylor College of Medicine and sanofi pasteur, the vaccines business of the sanofi-aventis Group, set out to test whether elderly people could be given higher doses of vaccine safely and whether the higher doses would increase their levels of antibody.

The trial, which was supported by NIH's National Institute of Allergy and Infectious Diseases, is described in the latest issue of the Archives of Internal Medicine. The investigators randomly put 202 adults 65 years of age or older into 4 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. All were followed for a month after vaccination to spot any vaccine-related side effects and to collect blood to evaluate how much antibody their bodies made.

The researchers found that participants in the highest-dose group had 44 to 79% higher levels of antibody than those who received the normal vaccine dose. The vaccine was well-tolerated at all dosage levels. While the higher doses of vaccine caused more mild side effects at the injection site, there weren't significant differences in symptoms such as fever or body aches.

Elderly Americans are among the most vulnerable to the serious complications of seasonal influenza because they tend to have more underlying diseases and weaker immune systems than younger people. This study suggests that giving the elderly a higher dose of vaccine may be a safe way to help better protect them from deadly bouts with the flu.

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Editor: Harrison Wein, Ph.D.
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NIH Research Matters is a weekly update of NIH research highlights from the Office of Communications and Public Liaison, Office of the Director, National Institutes of Health.

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