Giving elderly people age 65 and older a dose four times larger than the standard flu vaccine boosts the amount of antibodies in their blood to levels considered protective against the flu, more so than the standard flu vaccine does. The higher dose of vaccine generally resulted in approximately 30 percent to 80 percent more antibodies against flu, long considered a good measure of protection.

The immune system generally weakens as we get older, not only leaving people more vulnerable to infection but also reducing their ability to respond to vaccination. While some studies have questioned the effectiveness of the flu vaccine in older adults, the nation’s leading public health experts stress that it’s a worthwhile, even life-saving, measure. About 90 percent of the estimated 36,000 people who die from flu-related causes in the United States each year are 65 and older.

The conventional flu vaccine is a combination of three circulating strains of flu, with each component consisting of 15 micrograms of material designed to evoke an immune response to protect a person against a particular type of flu. In the study headed by Falsey and conducted at 30 sites around the country in fall 2006, physicians compared the immune response brought about from a traditional flu vaccine compared to that from a vaccine shot containing four times as much material – 60 micrograms of material known as hemagglutinin for each of the three components.

In the study of people age 65 and older, the larger dose was given to 2,575 participants, while 1,262 subjects received the standard dose. Scientists checked the level of antibodies in the blood of the participants one month later. Generally, the large-dose vaccine increased the number of flu antibodies in study participants on average from about 30 to 80 percent. The level of such antibodies in the blood has long been considered a good gauge of how protected people are against the flu.

A greater percentage of people who received the high-dose vaccine had the typical side effects associated with the flu shot, including redness, swelling, and pain at the site of the injection, but the symptoms generally did not last longer than three days.

“These are the people at the highest risk for becoming very sick from influenza, and we saw significant improvement in the immune response in many of these people,” said Falsey. “This is very encouraging.”

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