Lab testing human West Nile vaccine

KANSAS CITY, Mo. -- Veterinarians having been advising horse owners in recent summers to vaccinate their animals against West Nile virus. But no such vaccine is available for humans, for whom long sleeves and mosquito repellent provide the best protection against the disease.

That could change sometime in the next several years.

Sixty young adults in the Kansas City area have become the first subjects for tests of a human vaccine for West Nile, the mosquito-borne virus that sickened more than 8,700 people and killed more than 200 in the United States this year.

Tests of the vaccine, made by Cambridge, Mass.-based Acambis, began in late October.

Three groups of 15 volunteers each are receiving varying doses of the vaccine. A fourth group gets a government-approved yellow fever vaccine that was used to create the West Nile vaccine.

Researchers will follow the subjects for a year to see how well their immune responses to West Nile virus hold up.

Acambis began work on the West Nile vaccine in 1999, soon after the disease first appeared in the United States. The company is best known as the maker of the new generation of smallpox vaccine.

Most people infected do not become ill. But the virus can cause fevers, aches and -- in rare cases -- potentially lethal brain inflammations.

"Given the explosion of West Nile, my belief is the number of cases will increase. It wouldn't surprise me to see 50,000 or more cases a year," said Thomas Monath, chief science officer for Acambis.

Monath doesn't expect health departments to issue broad recommendations for the public to seek vaccinations. The vaccine could become popular, however, among people who spend lots of time outdoors or who live in areas where West Nile has reached epidemic levels.

"At the current level of concern, hundreds of thousands of people may seek it," Monath said.

The vaccine faces several years of human testing before it would become available to the public, Monath said.

"We're looking at safety and how well it's tolerated and the immune response to the vaccine," he said.

The vaccine already has proven effective in experiments on monkeys. A dozen were immunized and had West Nile virus injected into their brains. None became ill. Six monkeys that weren't given the vaccine developed encephalitis.

Acambis will next study the vaccine in older adults and eventually conduct a large trial involving several thousand subjects.

The company received a $3 million federal grant in 2000 to develop the vaccine, but Monath estimated the total cost would reach $50 million to $100 million.