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Jul 23, 2007 11:59 pm US/Mountain
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Why Isn't There A Vaccine For The West Nile Virus?
by Alan Gionet
FORT COLLINS, Colo. (CBS4) ―
Eight years ago, the West Nile Virus showed up in metropolitan New York. It was insidious. People with severe cases would get encephalitis - a swelling of the brain. It was a killer that had to be stopped.
West Nile was first discovered in Uganda in 1937. It's primarily found in Africa and the Middle East.
Experts believe Colorado has the potential for a severe year, because they've found the virus in mosquitoes collected in several areas, especially in North-Central Colorado.
There's one positive about the West Nile Virus in Colorado in 2007. Scientists think once an area has had a severe West Nile outbreak, as Colorado did in 2003 when more than 60 people died, the chances for another big outbreak of disease, may for some reason, be lessened. They don't know why.
That's one of the things they're studying. Another is a vaccine. Much of the research is being done at the Centers for Disease Control and Prevention lab in Fort Collins.
Other vaccines are being developed by private industry. The one that's furthest along in development in being produced by the biotech company, Acambis. It is now in phase II trials. There must be at least three trial phases successfully completed before vaccines are approved for human use.
"Well, it certainly will be several years before a West Nile Virus vaccine will be available for use in humans," says CDC medical epidemiologist Dr. Marc Fischer.
There are a total of four vaccines in development. There have been no significant delays in development. The West Nile Virus holds no particular challenges like the elusive HIV; it just takes time.
The effort didn't start until West Nile showed up in the U.S. in 1999.
"We find horses that get vaccinated very very rarely get West Nile disease," says veterinarian Dr. Barbara Page of The Colorado Equine Clinic in Littleton.
It's a live virus type of vaccine. But the process of approving a vaccine for use in animals is much less rigorous than it is for humans. There is also a new breed of vaccine, a DNA vaccine approved for use in horses, but it's not being produced for market.
DNA vaccines hold great promise. Experts take a tiny piece of genetic code and place it into harmless E. coli bacteria where the vaccine is produced.
CDC research microbiologist Dr. Jeff Chang is working on a DNA vaccine for West Nile in Fort Collins. Chang says the cheaper DNA vaccine is looking promising.
"It's actually much simpler than live virus vaccine," says Chang.
If it were approved now, it would be the first DNA vaccine approved for human use. But it too, is years away. It's clinical trials are just getting started.
Dr. Fischer says there are also good questions about how any vaccine that gets approval would be used. About 80 percent of those who get the virus suffer little effect. Twenty percent get a nasty illness. One percent get severe cases.
The CDC is studying how any vaccine might be used.
"So this may be a vaccine we would use if it were ever developed, more like an influenza vaccine where we target people who are particularly at risk for bad disease," says Fischer.
Acambis wants to make its vaccine available for wide use. But if the government recommends a narrow vaccination program, that may limit profitability for any company that might produce it.
"Manufacturers always have to make a decision about there's a large enough market and whether they can make this vaccine for this market," says Fischer.
There's time for the CDC to study it with approval and production still several years away.
Additional ResourcesHere are some tips to prevent getting bit by a mosquito:
• Avoid outdoor activities at dusk and dawn when mosquitoes are most active.
• Use insect repellent on exposed skin when you go outdoors. Use an EPA-registered insect repellent such as those with DEET.
• Get rid of standing water where mosquitoes can breed.
• Larvacide can be placed in standing water to kill mosquito larvae.
Health officials ask for people who come across dead crows, blue jays, magpies and ravens to contact the Colorado Health Department.
• For more information on West Nile virus and prevention, call the Colorado Health Department at (877) 462-2911 or visit
cdphe.state.co.us.
• The Colorado Department of Public Health and Environment also has information online at
www.fightthebitecolorado.com.
• The Centers for Disease Control and Prevention has information in a
special section of their Web site.
(© MMVII CBS Television Stations, Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)