As West Nile Virus Cases Rise, Vaccine Still Far Off

Would a Vaccine Be Cost-Effective?

The inconsistency of the virus throws a big wrench into another critical factor: the commercial viability of a vaccine.

A 2006 study by the CDC concluded that, at least according to incidence rates at the time, universal vaccination would not be cost-effective.

The study's probability estimates included statistics from 2002, when 2942 neuroinvasive West Nile virus disease cases were reported from 36 states and the District of Columbia.

Although this year's incidence rates are high, West Nile virus rates for the years between 2002 and 2012 again underscore the unpredictability of outbreaks. Just last year, for instance, there were only 486 cases of neuroinvasive disease and 43 deaths in the United States. In 2010, there were 629 neuroinvasive cases and 57 deaths, according to the CDC.

With universal vaccination an unlikely scenario, any vaccine development would probably move in the direction of inoculation for those who are at the highest risk for serious illness from the virus, and efforts by the CDC to better define those populations are ongoing, Dr. Hills said.

"The CDC is working to consider and define high-risk populations that could be targeted and which groups would be cost-effective," she said.

Potential high-risk groups that could be targeted include those in older age groups or with certain medical conditions such as hypertension, kidney disease, diabetes and organ transplant patients.