June 20 (Bloomberg) -- Elderly people who received a flu shot under the skin instead of into a muscle were better protected against the deadly viruses, according to a study that may help prevent sickness and death in one of the most vulnerable groups.

Researchers at Sanofi Pasteur, the vaccines unit of Paris- based Sanofi-Aventis SA, found people aged 60 to 94 given the shot under the skin using a short, thin needle were about 7 percent better protected against flu than those who received Sanofi's Vaxigrip shot in a muscle with a conventional needle. The findings were presented today at the International Congress for Infectious Diseases in Kuala Lumpur.

The study may lead to changes in the way doctors vaccinate the elderly, whose immune systems are less responsive to infections than younger adults, said Melanie Saville, who led the study. Previous research has shown flu vaccines protect as much as 60 percent of elderly people, compared with 90 percent of younger adults, she said.

``What's new with this vaccine is the system,'' Saville said in an interview yesterday. ``The idea of this is to have something any practitioner can use.''

Seasonal flu kills about 36,000 people in the U.S. each year, and causes a further 200,000 to be hospitalized, according to the Centers for Disease Control and Prevention. About 90 percent of deaths and half of hospitalizations are among the aged, the CDC says.

Smaller Needle

Saville and colleagues used a so-called microinjection device, with a 1.5 millimeter-long needle, to give 2,612 people a shot containing three different flu viruses into the bottom layer of their skin. A further 1,089 people got a conventional jab in an arm muscle.

Almost 7 percent more of those who received the shallower shot had a fourfold increase in infection-fighting antibodies compared with those who received the conventional vaccine, signaling they were protected against flu. Side effects were similar for both groups.

The approach may work better than traditional intramuscular vaccines because the nerve endings that transport antibody- stimulating antigen to the immune system are more prevalent in the skin than in muscles, Saville said.

Easier Device

The device, developed by Franklin Lakes, New Jersey-based Becton, Dickinson & Co., will make it easier for doctors to administer intradermal shots, Saville said. Currently they use conventional needles at a narrow angle, a tricky procedure that can easily go wrong. Sanofi is considering using the device for other vaccines, Saville said.

The findings follow previous studies in adults, which showed intradermal vaccines give a similar level of protection to intramuscular shots, using less antigen.

Sanofi is relying on vaccines to bolster revenue as it faces slowing growth in its larger drugs unit. The company will lose patent protection on products accounting for almost half of sales by the end of 2012. One of the medicines it was expecting to replace revenue, the weight-loss pill Acomplia, failed to win approval in the U.S. because of safety concerns.

The European Medicines Agency is reviewing the results, and may approve the technique by the end of the year, Saville said.

To contact the reporter on this story: Simeon Bennett in Singapore at sbennett9@bloomberg.net

Last Updated: June 20, 2008 02:52 EDT