Drug companies cautious on vaccine for West Nile

As public concern about West Nile virus has intensified, so has the push to create a vaccine.

Several drug companies are considering developing new medical protections against the virus, including Emeryville, Calif.-based Chiron Corp.

But even though West Nile might look like a solid business opportunity as it spreads to new parts of the country, drug makers are mindful of what happened with Lyme disease, which didn't produce the windfall that had been expected. Although Lyme disease, spread by a tick bite, remains prevalent in wooded areas of the Northeast and upper Midwest, the only vaccine against the illness was discontinued in 2002 because of low demand.

So drug companies are approaching West Nile virus with caution.

Chiron, in the early stages of research, is waiting to see how far the disease spreads before committing to a full-scale effort.

"We have one eye in the lab and the other on the virus," Chiron spokesman John Gallagher said.

The stakes for the companies are big. The market for a vaccine could exceed $300 million, according to some estimates.

Beyond the economics of it, there is a sense of urgency from a public health standpoint.

Although most people with West Nile virus don't get sick, the disease can be deadly. The virus has killed more than 400 people nationwide since 1999.

Elderly people and those with weakened immune systems are most susceptible. One in 5 people who contract it develops symptoms, such as fever and muscle aches. About 1 in 150 infected people suffers the worst form of the disease, an inflammation of the brain. There is no treatment for the virus.