Progress Seen on West Nile Vaccine

Small studies of a possible vaccine against West Nile virus could begin within months and a vaccine for the people most at risk of dying from the virus could be available in three years, federal scientists told Congress on Tuesday.

The experimental vaccine is built on the long-used vaccine against yellow fever, a cousin of the West Nile virus. Scientists are hopeful it will prove safe to use, as well as provide protection for the elderly, who are at highest risk for getting encephalitis if they are infected with the virus.

West Nile virus first appeared in the United States in 1999 but caused an epidemic this year. So far, the federal Centers for Disease Control and Prevention has counted more than 1,900 infections and 94 deaths.

But only one out of every 150 to 200 people who are infected actually become seriously ill. Most either have mild flu-like symptoms or no symptoms at all.

That has actually complicated scientists’ ability to tell if West Nile can be transmitted through the blood supply. A recent infection in a woman who received blood from a West Nile-infected donor suggests that can happen, but the risk is believed low. Still, the Food and Drug Administration is pushing blood banks to develop tests that would detect the virus in donated blood.

Studies in animals suggest that immunity to other similar viruses, such as yellow fever and dengue fever, also provides protection against the virus, said Dr. Anthony Fauci of the National Institutes of Health. Based on that knowledge, scientists have put genes from the virus into the structure of the yellow fever vaccine. Meanwhile, people’s best defense is to wear mosquito repellent containing the chemical DEET and to eliminate all standing water around their homes.

“Most mosquitoes transmitting this virus live in the suburban backyard,” said CDC director Dr. Julie Gerberding.