Lenexa ? Veterinarians have 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 at the PRA International clinic in October.

Three groups of 15 volunteers each are receiving varying doses of the West Nile vaccine. A fourth control 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. The vaccine is intended to offer immunity within 10 days after a shot.

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 being stockpiled by the federal government.

West Nile virus, to which horses are especially vulnerable, is spread to people by mosquitoes that pick it up when they bite infected birds. Most people infected do not become ill. But the virus can cause fevers, headaches and muscle aches and — in rare cases — potentially lethal brain inflammations.

“Given the explosion of West Nile, my belief is the number of cases will increase,” 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.