West Nile Horse Vaccine Comparison Chart

Key Takeaways

• West Nile virus (WNV) is a mosquito-borne disease that can cause serious neurologic illness in horses, making vaccination an important part of equine disease prevention.
• The American Association of Equine Practitioners (AAEP) classifies the West Nile vaccine as a core vaccine recommended for every horse in North America, regardless of age, breed, or use.
• Horses receiving their first West Nile vaccination generally require an initial vaccine series followed by regular boosters, with timing based on vaccine label directions and individual risk.
• Annual West Nile vaccine boosters are typically given before mosquito season, while horses in areas with prolonged mosquito activity or other risk factors may benefit from more frequent vaccination.
• West Nile vaccines for horses are available as standalone or combination vaccines that can also provide protection against disease such as encephalomyelitis, tetanus, influenza, and equine herpesvirus.

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Your horse is part of the family, and keeping them current on their West Nile virus (WNV) vaccine is one of the most important things you can do for their health. WNV is spread by mosquitoes that pick up the virus from infected birds and pass it along to horses, humans, and other mammals. Since the virus first appeared in North America in the late 1990s, it has become established in nearly every U.S. state, as well as most of Canada and Mexico. Horses make up roughly 97 percent of all reported non-human mammalian WNV cases, which is exactly why the American Association of Equine Practitioners (AAEP) classifies WNV vaccination as a core vaccine — one every horse in North America should receive, regardless of age, breed, or how they're used.

Vaccination dramatically lowers your horse's risk of developing viremia and severe neurologic disease. It isn't a 100 percent guarantee, but a properly vaccinated and boostered horse has a much better chance of avoiding infection, and a much better outcome if they're exposed. Horses that do develop clinical signs face a case fatality rate of roughly 33 percent, and many that survive still show lingering gait or behavioral changes months later — which is exactly why staying current on this vaccine matters so much.

Below, we compare the current lineup of WNV vaccines for horses so you can see how they stack up, followed by guidance on timing and a few of the questions we hear most from horse owners.

When Should Horses Get the West Nile Vaccine?

Timing comes down to whether your horse has been vaccinated before.

If your horse has never been vaccinated for WNV, or you don't know their vaccination history, they'll need a primary series: two doses, typically spaced 3 to 4 weeks apart (check your specific vaccine's label, since some call for up to 6 weeks between doses). Foals follow a different schedule: usually a 3-dose series starting between 3 and 6 months of age, timed around their dam's vaccination status and the local mosquito season.

If your horse has already completed a primary series in a previous year, they just need an annual booster, ideally given in spring before mosquito season ramps up in your area.

Because mosquito season looks different depending on where you live, timing isn't one-size-fits-all. Horses in warmer climates with longer or year-round mosquito activity — the Gulf Coast, the Southwest, and parts of the South — are often better protected with a booster every six months rather than once a year. The same goes for young horses under 5, seniors over 15, and pregnant mares, who tend to be more susceptible and may benefit from more frequent vaccination. Your veterinarian is the best resource for building a schedule that matches your horse's age, health, and where you live.

Pregnant mares and foals need a bit of extra care in the planning. A mare who's already vaccinated should get a booster 4 to 6 weeks before foaling, which helps pass protective antibodies to the foal. If she's never been vaccinated, most vets recommend starting the primary series right away, ideally before she's bred. Foals typically begin their own primary series between 3 and 6 months of age, with the exact timing depending on the mare's vaccination status and how active mosquitoes are in your area. Your vet can help you map out the safest schedule for a broodmare or new foal.

Comparison Chart: West Nile Vaccines for Horses

Here's how the most common WNV vaccines for horses compare:

Vaccine Name	Manufacturer	Additional Protection Against	Earliest Age	Repeat Dose In	Annual Booster
Equi-Jec 6	Boehringer Ingelheim	Eastern and Western Encephalomyelitis, Influenza, Herpesvirus, Tetanus	4 months	3 to 4 weeks	yes
Equi-Jec 7	Boehringer Ingelheim	Eastern, Western and Venezuelan Encephalomyelitis, Influenza, Herpesvirus, Tetanus	4 months	3 to 4 weeks	yes
Equi-Jec WNV	Boehringer Ingelheim		4 months	3 to 4 weeks	yes
Equi-Jec WNV + EWT	Boehringer Ingelheim	Eastern and Western Encephalomyelitis, Tetanus	4 months	3 to 4 weeks	yes
Prestige 3 + WNV	Merck	Eastern and Western Encephalomyelitis, Tetanus	6 months	3-4 weeks	yes
Prestige 5 + WNV	Merck	Eastern and Western Encephalomyelitis, Rhinopneumonitis (Equine Herpesvirus types EHV-1 and EHV-4), Influenza and Tetanus	6 months	3-4 weeks	yes
Prestige WNV West Nile Virus	Merck		6 months	3-4 weeks	yes
Vetera EWT + WNV	Boehringer Ingelheim	Eastern and Western Encephalomyelitis, Tetanus	4 months	3-4 weeks	yes
Vetera Gold XP	Boehringer Ingelheim	Eastern and Western Encephalomyelitis, Rhinopneumonitis (Equine Herpesvirus types EHV-1 and EHV-4), Influenza, Tetanus	4 months	3-4 weeks	yes
Vetera Gold XP + VEE	Boehringer Ingelheim	Eastern, Western and Venezuelan Encephalomyelitis, Rhinopneumonitis (Equine Herpesvirus types EHV-1 and EHV-4), Influenza, Tetanus	4 months	3-4 weeks	yes
Vetera VEWT + WNV	Boehringer Ingelheim	Eastern, Western and Venezuelan Encephalomyelitis, Tetanus	4 months	3-4 weeks	yes
Vetera West Nile	Boehringer Ingelheim		4 months	3-4 weeks	yes
West Nile Innovator	Zoetis Animal Health		10 months	3-4 weeks	yes
West Nile Innovator EWT	Zoetis Animal Health	Eastern and Western Encephalomyelitis, Tetanus	10 months	3-4 weeks	yes
West Nile Innovator + VEWT	Zoetis Animal Health	Eastern, Western and Venezuelan Encephalomyelitis, Tetanus	10 months	3-4 weeks	yes

Standalone WNV vaccines like Prestige WNV, Vetera West Nile, Equi-Jec WNV, and West Nile Innovator protect against West Nile virus only. If your horse also needs protection against sleeping sickness (encephalomyelitis), tetanus, influenza, or rhino, a combination vaccine can cover multiple diseases in a single shot. Ask your vet whether a combination product makes sense for your horse.

Frequently Asked Questions

When should horses get the West Nile vaccine?

Most horses should get their annual booster in spring, before mosquito season picks up in your area. If your horse has never been vaccinated, start the primary series as early as you can so it's complete before mosquitoes become active.

Is the West Nile vaccine required?

There's no federal law requiring it, but the AAEP classifies WNV vaccination as a core vaccine — recommended for every horse in North America, regardless of age, breed, or use. Some boarding facilities, show venues, and events do require proof of current vaccination, so it's worth checking with your barn or event organizer.

How often does a horse need a booster?

Once your horse has completed their primary series, an annual booster is the standard recommendation. Horses in warm climates with year-round mosquito activity, along with young, senior, or pregnant horses, may need boosters every six months instead. Ask your vet what makes sense for your horse.

Can horses still get West Nile virus after vaccination?

It's possible, though uncommon. No vaccine offers complete protection, but vaccinated horses that are exposed tend to have a much lower risk of severe disease, and better outcomes if they do get sick. Most breakthrough cases happen in horses who are overdue for a booster or who never completed their primary series in the first place. Staying current on boosters is what keeps that protection strong. Immunity from these vaccines is only labeled to last about 12 months.

What are the symptoms of West Nile in horses?

Early signs can look like a mild flu: fever, muscle twitching, and low energy. As the virus moves into the nervous system, symptoms can progress to stumbling or weakness (especially in the hind end), incoordination, tremors, a drooping lip, teeth grinding, and in severe cases, difficulty standing or seizures. If you notice any of these signs, call your vet right away rather than waiting to see if they pass. Early treatment gives your horse the best chance at a full recovery, and WNV has a case fatality rate of around 33 percent in horses that develop clinical signs.

Sources: American Association of Equine Practitioners (aaep.org), and Valley Vet Supply's current equine vaccine catalog.

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