Byron Chism goes through the process of identifying the sex, species and count of the captured mosquitoes at Dallas County Mosquito Lab to test some of them for West Nile virus. Photo by Evans Caglage/The Dallas Morning News.
By Cortney Coleman
For Reporting Texas and the Dallas Morning News
AUSTIN — If you were a horse, you could be vaccinated against the West Nile virus that has killed more than 160 people this year nationwide.
The reasons: It’s a lot easier to get vaccines approved for horses, and vaccinating horses is profitable for drug makers. Vaccines for humans must clear a long, expensive gantlet of testing and approvals through the Food and Drug Administration, and drug manufacturers haven’t regarded the human market as a place to make enough money to justify producing a vaccine.
This year’s outbreak is the worst in recent decades, and it centered on North Texas, with more than 80,000 estimated infections in the region. Most cases were not serious, but hundreds were, and in Dallas County, 16 deaths were reported.
The severity has revived interest in protecting people from West Nile, but it will be years until a human vaccine hits the marketplace, assuming it ever does.
“The first problem is market, and the second is technical challenges,” says Elliot Parks, chief executive of Hawaii Biotech, which is working on a human vaccine. “But most companies blame the market before anything else.”
West Nile arrived in the U.S. in 1999 and is transmitted by mosquito bites. Horses and humans have been the main victims.
According to the American Association of Equine Practitioners, more than 25,000 cases have been recorded. The Centers for Disease Control and Prevention says more than 30,000 humans have caught the potentially fatal disease in the same period.
Four horse vaccines have been approved by the U.S. Department of Agriculture, and the vaccine is a “core” medication recommended for all horses, according to the USDA’s Animal and Plant Health Inspection Service.
After a spike in West Nile cases in 2003, several companies began working on human vaccines, but later dropped the projects because they weren’t considered profitable. According to the CDC, almost 7,000 people caught the disease that year, and 264 died.
Crucell N.V., a Dutch biotech firm, scrapped its vaccine in 2008 because it wasn’t “as attractive as other products in Crucell’s pipeline,” the company said at the time.
The CDC concluded in a 2006 “cost-effectiveness” study that universal human vaccination against West Nile wouldn’t save money “unless disease incidence increases substantially over what has been seen in the past six years.”
The current outbreak coincides with near-perfect conditions for mosquitoes in some areas, and it’s difficult to say when that will happen again or where an outbreak will strike. This year, nearly 70 percent of cases have come from eight states — Texas, California, Louisiana, Mississippi, South Dakota, Oklahoma and Illinois. Texas accounted for a third of all cases.
“That’s a challenge for West Nile,” said CDC epidemiologist Ingrid Rabe. “It goes up and down every year and has a very unpredictable nature. So it’s hard to say if it will recur every year.”
At least two companies are moving ahead with a human vaccine. Sanofi Pasteur USA is testing a vaccine called Chimerivax-WNV, and Hawaii Biotech is hoping to develop its vaccine for older people who might be more vulnerable to the virus. Even if both companies stick with their projects, it will be years before humans have the same protection as horses.
“The vaccine development process is a lengthy one, often lasting 10 to 15 years,” Rabe said in an email.