When it comes to getting shots, a single needle prick might seem like a better idea compared to multiple pokes. But when it comes to your horses’ West Nile virus (WNV) vaccinations, multiple injections might be the way to go: Researchers recently tested horses’ serologic (blood) response to six WNV vaccination regimens and found some significant differences between horses’ immune responses when vaccinated with a combination WNV vaccine versus a WNV vaccine administered separately but at the same time as other vaccines.

Kevin G. Hankins, DVM, MBA, a senior veterinarian in Equine Veterinary Operations with Zoetis, described the full research, results, and recommendations during a presentation at the 2013 American Association of Equine Practitioners’ Convention, held Dec. 7-11 in Nashville, Tenn.

To test the immune response triggered by six different vaccine regimens, Hankins and colleagues separated 280 WNV-free Quarter Horses—aged 2 to 17 years—into seven groups. In the study they:

• Vaccinated the horses in three treatment groups with three different commercially available vaccines that contained WNV, EEE, WEE, and tetanus antigens in a single shot;
• Vaccinated the horses in three other treatment groups with a WNV-specific vaccine concurrently with a combination EEE, WEE, and tetanus vaccine; and
• Treated one group with saline; these horses served as unvaccinated controls.

The team vaccinated all horses twice, 21 days apart, with their assigned treatment regimen. The researchers collected blood samples on six different occasions throughout the 42-day study to evaluate the horses’ WNV antibody titer levels