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Posted by MamaClaire on September 19, 2002 at 11:55:47:

In Reply to: Re: West Nile - a manufactured crisis? posted by Deerhounds on September 18, 2002 at 19:06:28:

:Something is presented either a FACT, like "horses who are vaccinated are immune," or it's presented as an OPINION. Facts need evidence, obviously opinions don't.

Totally agree, Christie. I asked my fav equine vet to explain to me about what it means for the WNV vax to be approved but efficacy unknown, according to CDC. Dr. Ramey said I could post his reply, and he might check in too to see if he can help:

My question:What does this mean? I thought the Dept of Agriculture or somebody made the
> drug company prove DOI for rabies, I guess because of the risk to public
> health. So is that what is meant by "effectiveness" is unknown? No testing
> for DOI because of no known threat of human-horse transmission?
>
> Or, am I mixing apples and oranges? Does "effectiveness" mean something
> else? If so, on what basis was the vax recently approved?

Dr. Ramey's answer: Well, here's the thing. Animal vaccines are approved by the USDA and
human
vaccines are approved by the FDA. In order for a human vaccine to be
approved,
safety and efficacy trials have to be conducted. That is, the vaccine has
to
be shown not only to be safe, but also to prevent the disease.

This is not necessarily the case with veterinary vaccines. In the
particular case of the WNV vaccine, the manufacturer got a conditional
license
based on the fact that the vaccine did not appear to hurt any horses and
there
was a need for a vaccine. They did *not* have to show that the vaccine
actually prevented West Nile Virus in horses.

The company just released an abstract showing that vaccinated horses did
not develop virus in their blood when exposed to a viral challenge, whereas
most control horses did. The thing is, *none* of the horses in the trial
got
sick, so it does leave you wondering if the trial was conducted with a
sufficient dose of the virus.

Field studies would probably answer a lot of the questions about the
efficacy of the vaccine. However, my guess is that it will take a motivated
graduate student to do such a study, because the vaccine company would never
be
interested in any data that might show that the vaccine didn't work.

David Ramey, DVM

Follow Ups:

• that's exactly what my vet told me about the vaccine.... LisaT 09/20/02 (0)