West Nile Virus Vaccine Q&A

The following information is from Rocky Bigbie, DVM, a representative of Fort Dodge Animal Health, the company that manufacturers the West Nile virus (WNV) vaccine. Company officials recommend that horse owners consult with their own veterinarians to get more specific details about the threat to their horses.

What is the vaccination schedule in normal areas and areas under
outbreak conditions?

The vaccine is labeled for annual booster after the initial two-dose regimen.  In some areas, equine clinicians have recommended a more frequent, six-month interval based on very high risk, ie., outbreak situations.  This is a discretionary call after consultation with your local veterinarian.

Is the vaccine effective? Safe?

Yes to both questions. The conditional license assures safety to standards no less stringent than that for fully-licensed vaccines. Plus, extensive field use with millions of doses given has assured this assessment of safety. The efficacy of the product is based a laboratory test which gives “a reasonable expectation of efficacy.” West Nile virus, being a human pathogen, must be evaluated experimentally in an extremely careful fashion. Experimental challenge was not originally done for this reason; but, the in vitro analysis gives us reasonable expectation of efficacy. Additionally, field use seems to have bolstered the confidence that the vaccine is protecting horses. Eventually, an experimental challenge efficacy trial will confirm this efficacy.

How was the vaccine developed so quickly?

The vaccine was not really developed so quickly. Although much of the nation is only recently aware of the problems with WNV, the virus was isolated and available for research back in 1999. Fort Dodge Animal Health is devoted to the development of innovative vaccines. The WNV vaccine is consistent with that aggressive history. Also, this virus is similar to others for which similar vaccines have been made for years.

What field trials were done? 

A safety field trial was completed, as is done with all vaccines.  649 horses (were tested). Very good results. 

When do you expect full licensure? 

The data for full licensure has been obtained.  The USDA must now validate our experimental design and review the data.  We are hopeful that this will be completed soon, but we cannot predict the outcome of that review.

How many doses have been distributed and where?

Approximately four million doses—all over the U.S. and Canada. 

What is your current research focusing on?

Full license and combination vaccine efficacy and safety.

Where can horse owners and veterinarians get more information on  the vaccine?

http://www.Equinewestnile.com .

Is there anything else you would like to add about WNV and the vaccine? 

We are very confident in the product. 

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