Why Does My Horse Need Annual Vaccinations?

Ongoing exposure can cause a decrease in immune response and can impact horse health.

From AQHA Corporate Partner Zoetis

For disease pathogens that pose a high risk of infection for horses, annual vaccination is recommended. But many horse owners are asking, “Why?”

“It all has to do with immunologic memory. Immunologic memory is the body’s immune response against an infectious pathogen,” says Dr. Kevin Hankins, senior veterinarian for Zoetis Equine Technical Services. “The body reacts more quickly after the immune system has been primed with an initial series of vaccines. Despite the fact that vaccines produce immunologic memory, circulating vaccine-specific antibodies and immune cells in horses drop in concentration after a few months. Annual boosters help keep these numbers steady. A horse that is not vaccinated annually is very much at risk.”

As an AQHA member, you will become a part of the largest breed organization in the world. Join today!

For example, with West Nile virus, and eastern and western equine encephalomyelitis viruses (EEE/WEE), horses are continually exposed to mosquitoes that transmit these potentially deadly viruses. This ongoing potential for exposure means horses should receive annual boosters against West Nile, EEE and WEE prior to peak mosquito season.

“Depending on a horse’s risk to pathogen exposure, he may require more frequent boosters against respiratory viruses such as equine influenza virus and equine herpesvirus (rhinopneumonitis),” Dr. Hankins says.

The American Association of Equine Practitioners vaccination guidelines recommend that at-risk horses be vaccinated every six months.1 Horses at risk include those less than 6 years old, senior horses and horses that may be frequently exposed to respiratory viruses at shows, trail rides or other events.

Horses in closed herd situations may require fewer respiratory vaccines than horses competing or traveling to group activities. However, if you are traveling to events with one horse, be sure to vaccinate your whole herd, not just select horses.

Become an AQHA member today and gain access to all of the resources that membership has to offer. This includes registering and owning your very own American Quarter Horse!

“If you only vaccinate one horse in a group, other horses that are not immunized could get sick to the extent that the disease will overcome the effects of the vaccine in the protected horse,” Dr. Hankins says. “Vaccines are a key part of an overall biosecurity program. Only by vaccinating all horses in your herd is the potential for disease incidence decreased.”

As each horse has a unique set of needs, a standard one-size-fits-all equine vaccination program does not exist. Consult with your veterinarian to determine which diseases you should vaccinate your horse against, how often and at what time of the year. Be sure to vaccinate your horse with FLUVAC INNOVATOR® and WEST NILE-INNOVATOR® for the most trusted equine disease protection.2

The broad portfolio of equine vaccines and health care products from Zoetis is one you can rely on. To learn more, visit

1 American Association of Equine Practitioners. Vaccination Guidelines. 2012. Accessed Sept. 27, 2016.

2 Data on file, MDI sales data for WEST NILE-INNOVATOR and FLUVAC INNOVATOR as of 12/31/15, Zoetis LLC.

All trademarks are the property of Zoetis Services LLC or a related company or a licensor unless otherwise noted.

© 2016 Zoetis Services LLC. All rights reserved. FLU-00108