Horse Vaccination Schedule: Complete Guide for Every Horse Owner

Last updated: April 3, 2026

By: Miles HenryFact Checked

Getting your horse vaccination schedule right is the cheapest insurance you can buy. I’ve seen what EEE does to an unvaccinated horse — it’s fast, brutal, and usually fatal. After 30 years managing Thoroughbreds in Louisiana, this is the exact protocol I use to keep horses protected year-round.

A horse vaccination schedule is more than a list of shots — it’s a timed program built around your horse’s age, location, and real-world exposure risk. What protects a backyard horse in the Midwest won’t fully cover a racehorse on the Gulf Coast, and that difference matters.

Whether you’re building a program from scratch or tightening up your current routine, this guide gives you the exact schedule, timing, and regional adjustments needed to get it right.

Core Vaccines: Required for Every Horse

The American Association of Equine Practitioners (AAEP) identifies four vaccines as “core” — meaning every horse in North America should receive them regardless of age, use, breed, or location. These diseases are endemic, life-threatening, and in some cases have public health implications.

EEE / WEE (Encephalomyelitis)

EEE and WEE vaccines are almost always delivered as a combination product, typically alongside tetanus toxoid in a single injection. In the Gulf South — Louisiana, Mississippi, Florida, Alabama — EEE is not a “might happen” disease. It kills horses in this region every year. The AAEP recommends annual vaccination in spring; semi-annual vaccination is strongly advised in high-risk areas like Louisiana, where mosquito season stretches from early spring through late fall.

• EEE mortality in horses is 75–90% — the vast majority of horses that develop clinical EEE do not survive
• No antiviral treatment exists; supportive care may extend survival but rarely changes the outcome
• Previously unvaccinated adults need a primary 2-dose series (4–6 weeks apart) before moving to annual boosters
• Timing matters: vaccinate in early spring, before the first significant rainfall and warming that triggers mosquito activity

West Nile Virus (WNV)

West Nile virus has been actively transmitted in Louisiana every year since it was first detected in the state in 2002. The AAEP’s WNV vaccination guidelines recommend a primary 2-dose series for naïve horses (4–6 weeks between doses) followed by annual revaccination — with semi-annual intervals recommended for horses under age 5, performance horses, and horses in high-exposure regions like the Gulf Coast.

• Multiple vaccine types exist: inactivated whole virus, recombinant canarypox vector, and inactivated flavivirus chimera — all are effective when administered correctly
• WNV has no cure. Some horses recover with supportive care; approximately 30–40% of horses with severe neurologic disease do not
• Horses that survive severe WNV infection may have permanent neurological deficits
• In Louisiana, I vaccinate for WNV in February/March AND again in August — the late-summer booster aligns with peak Culex mosquito activity

Tetanus

Horses are among the most susceptible domestic animals to tetanus. The Clostridium tetani bacterium lives in soil everywhere horses live — any wound, puncture, or surgical incision is a potential exposure point. Annual vaccination with tetanus toxoid is inexpensive, highly effective, and should never be skipped.

• Annual booster covers routine protection; horses that sustain a penetrating injury or go into surgery should receive an additional booster if their last dose was more than 6 months ago
• A horse that has never been vaccinated or has unknown history should receive a primary 2-dose series (4–6 weeks apart) before moving to the annual schedule
• Tetanus is nearly always fatal in horses if not caught and treated within hours of first symptoms — and clinical tetanus is difficult to treat even with antitoxin

Rabies

Rabies is invariably fatal once symptoms appear — in horses and in humans exposed to an infected horse. Louisiana has a significant wildlife rabies population (raccoons, skunks, bats, foxes), and horses kept on pasture with access to wooded areas are at real risk. Annual vaccination is inexpensive and the consequences of skipping it are catastrophic.

• Any horse that bites or scratches a human may trigger a public health investigation — vaccination history matters in these situations
• Horses in wooded or semi-rural areas (essentially all of south Louisiana) face higher exposure risk from infected wildlife
• A single annual dose provides full protection; no booster is needed at injury

Risk-Based Vaccines: Gulf Coast & Southeast

Risk-based vaccines are recommended based on a horse’s individual exposure risk — where they live, how much contact they have with other horses, whether they travel to shows or events, and regional disease prevalence. In Louisiana and the Gulf Coast, several risk-based vaccines effectively function as de facto necessities given local conditions.

Equine Influenza

Equine influenza spreads rapidly through respiratory droplets — one coughing horse at a sale barn, show, or fairground can infect dozens of horses within hours. Any horse that leaves your property for any reason, or comes into contact with horses that travel, is at meaningful risk.

• The AAEP recommends vaccination every 6 months for horses at risk of exposure — which in practice means most horses in Louisiana that attend any events or share facilities with other horses
• Two formats are available: injectable inactivated vaccine and intranasal modified-live vaccine (FluAvert). Many vets prefer the intranasal for performance horses as it produces stronger mucosal immunity
• Low-exposure horses (permanently pastured, no contact with outside horses) may be adequately covered with annual vaccination

Equine Herpesvirus (Rhinopneumonitis — EHV-1 and EHV-4)

EHV-1 and EHV-4 cause respiratory disease, abortion in pregnant mares, and in rare but devastating cases, equine herpesvirus myeloencephalopathy (EHM) — a neurological form that can cause paralysis and death. EHV is endemic in the horse population and reactivates under stress.

• Performance horses: Boost every 3–4 months — the stress of competition and travel suppresses immunity and triggers latent infections
• Broodmares: Vaccinate at months 5, 7, and 9 of pregnancy with the EHV-1 abortion vaccine (not all EHV products are labeled for this purpose — confirm with your vet)
• Pleasure horses with low exposure: Semi-annual vaccination is generally adequate
• Note: existing EHV vaccines provide protection against respiratory disease and reduce abortion risk, but do not fully prevent neurological EHM — biosecurity remains critical

Strangles (Streptococcus equi)

Strangles is one of the most common equine infectious diseases in the world — highly contagious, extremely persistent in the environment, and capable of shutting down a barn for months if it gets in. I’ve seen it move through a 30-horse facility and infect 80% of the horses because one new arrival wasn’t properly quarantined.

• Injectable vaccine: Reduces severity of disease but doesn’t prevent infection in all horses
• Intranasal modified-live vaccine (Pinnacle I.N.): Produces stronger mucosal immunity at the point of entry; generally preferred for horses with high exposure risk
• Important: Don’t vaccinate horses that have been recently exposed or are in an active outbreak — the intranasal vaccine can cause disease in immunocompromised or recently infected horses. Always consult your vet about timing
• New horses entering a property should be quarantined for a minimum of 2–3 weeks and ideally titer-tested before introduction to the herd

Potomac Horse Fever (PHF)

Potomac Horse Fever is caused by Neorickettsia risticii — transmitted when horses accidentally ingest infected aquatic insects (caddisflies, mayflies, damselflies) that emerge near standing water. In Louisiana, this is highly relevant. Bayous, creeks, flooded pastures, and the proximity of most Louisiana horse properties to water mean PHF exposure risk is real and recurring.

• Clinical signs include severe diarrhea, fever, depression, and laminitis — PHF can be fatal if not treated promptly
• Vaccinate in early spring before aquatic insect emergence (February–March in Louisiana) and again in late summer (August) when a second insect emergence peak occurs
• Vaccine efficacy is moderate — PHF vaccination reduces severity but does not prevent all infections. Keep turnout away from creek banks and standing water during peak emergence

Complete Vaccination Schedule by Horse Type

Adult Horses (Previously Vaccinated, Known History)

The simplest scenario: an adult horse with a documented vaccination history and a current program in place. The goal is to maintain protective immunity by keeping boosters on schedule and adjusting risk-based vaccines when the horse’s use or exposure changes.

Senior Horses (15+ Years)

Senior horses often have reduced immune function — their response to vaccines may be less robust than younger horses, and they may be more susceptible to diseases even with vaccination in place. This doesn’t mean vaccinating less; it means vaccinating consistently and building a complete health program around it.

• Follow the same core vaccine schedule as adult horses — do not reduce frequency based on age
• Horses with PPID (Cushing’s disease) have suppressed immune function and may need semi-annual vaccination across the board — discuss with your vet
• Pre-vaccination bloodwork (including ACTH for PPID screening) is worthwhile for senior horses to confirm no underlying condition is compromising vaccine response
• Time vaccinations away from other stressors — dental procedures, major feed changes, or new herd introductions within the same week can suppress immune response
• For more on managing senior horses holistically: feeding senior horses, best senior feeds, and what actually determines lifespan

Broodmares

Broodmares have the most carefully timed vaccination schedule of any horse category. Pre-foaling vaccination is critical because foals are born without meaningful immunity of their own — they depend entirely on the antibodies in the mare’s colostrum for protection in their first weeks of life.

• 4–6 weeks before foaling: Booster all core vaccines (EEE/WEE, WNV, tetanus, rabies) — this primes the mare’s antibody levels at their highest point just before colostrum production
• 5th, 7th, and 9th months of pregnancy: EHV-1 abortion vaccine (use products specifically labeled for this purpose)
• Avoid vaccination in the first 90 days of pregnancy unless disease risk outweighs concern — first trimester is the period of highest susceptibility to vaccine-associated complications
• Mares vaccinated on schedule produce colostrum with high levels of antibodies that protect foals for their first 3–4 months of life

Foals

Foal vaccination timing depends entirely on whether the dam was properly vaccinated before foaling. Foals from vaccinated mares carry maternal antibodies that interfere with vaccine response in early life — those antibodies protect the foal but also block the foal’s immune system from responding to early vaccines.

For the full foal management context around these vaccine windows — including colostrum, passive transfer, and weaning timing — see our foal care guide for the first year.

Performance and Show Horses

Any horse attending shows, rodeos, fairs, sales, or events faces dramatically higher disease exposure risk than a horse that stays home. Travel stress suppresses the immune system, and exposure to hundreds of horses from different regions happens every weekend at active circuits.

• Influenza and EHV: every 3–6 months — the most important interval to tighten for active show horses
• All core vaccines: follow the standard adult schedule but consider semi-annual for WNV and EEE given additional stress and travel
• Many show facilities, horse shows, and competitions in Louisiana and surrounding states require documentation of current influenza and EHV vaccination for entry — keep vaccine records with your Coggins and health papers
• Time boosters 2–3 weeks before major events so full immunity develops before competition stress hits

EEE and West Nile: A Louisiana Owner’s Warning

I want to spend a moment on this specifically — not as a general vaccination discussion, but as something I’ve lived with for 30 years in south Louisiana.

In 2025, 11 horses in Louisiana tested positive for EEE across multiple parishes. One of those horses also tested positive for West Nile virus. These weren’t horses in some far-off state where the disease is unusual — they were in the same region where most of my readers keep horses, fed by the same waterways, bitten by the same mosquitoes. LSU Veterinary Medicine has called EEE one of the most underappreciated lethal equine threats in the region.

The Louisiana Department of Health has documented active West Nile transmission every year since 2002 — and the human case data severely undercounts animal exposure because most horses aren’t tested unless they’re showing clear neurological signs. The mosquito population that carries WNV and EEE in Louisiana is not seasonal in the same way as northern states — activity begins in February and doesn’t end until December in mild years.

My protocol for Louisiana horses: EEE/WEE/Tetanus and WNV in February, before the first major warming event. A second WNV booster in August, before peak late-summer mosquito activity. This is not excessive — it’s the minimum I’d recommend for any horse kept outdoors in the Gulf South.

Mosquito Reduction Alongside Vaccination

Vaccination is the primary defense, but reducing mosquito breeding on your property meaningfully lowers exposure. In Louisiana, complete elimination isn’t possible — but you can reduce the population around your barn and paddocks:

• Eliminate standing water: overturn buckets, clean water troughs weekly, and address low spots that hold water after rain
• Use quality fly sheets and fly masks during peak hours (dusk and dawn) — they don’t prevent all mosquito contact but reduce it significantly
• Consider stalling horses overnight during active outbreak alerts in your parish
• Report suspected EEE or WNV cases to your state veterinarian immediately — early surveillance data helps neighboring owners take preventive action

New Horses and First-Year Protocols

Any horse arriving at your property with unknown vaccination history — or whose last vaccines you can’t verify — should be treated as unvaccinated and started on a primary series. This is one of the most commonly skipped steps in horse management, and it’s how diseases like strangles and influenza enter established herds.

• Quarantine first: Isolate the new arrival from your existing horses for a minimum of 2 weeks — ideally 4 weeks. Observe for respiratory signs, nasal discharge, fever, and swollen lymph nodes before any herd contact
• Vet check on arrival: Schedule a veterinary examination that includes a physical assessment, Coggins test (required by law for equine transport in Louisiana), and vaccination planning
• Primary series for all core vaccines: Naïve adult horses need a 2-dose primary series (4–6 weeks apart) for EEE/WEE, WNV, and rabies before moving to the annual schedule. Tetanus toxoid follows the same protocol
• Risk-based vaccines: Assess exposure history, intended use, and regional risk to determine which additional vaccines are needed
• Document everything: Start a vaccination record the day the horse arrives. This record is required for many show entries, interstate transport, and competition events — and it protects you legally if a disease question arises

Horse Vaccination Schedule and Your Annual Health Program

Vaccination doesn’t exist in isolation. An effective equine preventive health program combines vaccination with parasite management, dental care, hoof care, and nutrition into a coordinated annual schedule. These components reinforce each other — a horse carrying a heavy parasite load will have a diminished immune response to vaccines; a horse with painful dental problems won’t maintain the body condition that supports good health overall.

Parasite Management

Strategic deworming based on fecal egg counts has largely replaced the old calendar-based rotation approach. The goal is to target the specific parasites present in your horse at meaningful levels, rather than blanket-treating on a fixed schedule that builds resistance. Learn the signs that your horse may need deworming and discuss a fecal egg count program with your vet.

In Louisiana, the warm, humid climate supports year-round parasite activity — strongyles, tapeworms, and bots all have active periods that require targeted treatment. See our complete guides to horse digestive health and parasite control for a full breakdown.

Dental Care

Annual dental exams — and floating as needed — are as fundamental to equine health as vaccination. A horse that can’t properly chew can’t adequately absorb the nutrients it needs to support immune function. Senior horses often need dental work every 6 months. Dental exams are typically coordinated with spring vet visits, making them easy to schedule alongside vaccinations and parasite management.

Coggins Testing

Equine Infectious Anemia (EIA) testing via the Coggins test is required by Louisiana law for all horses being transported across state lines or attending public events. Annual Coggins testing is standard practice — your vet will typically run it at the spring health visit alongside vaccinations. Keep a current Coggins certificate in your trailer at all times.

Spring Health Visit: What to Combine

The annual spring vet visit is the most efficient opportunity to address multiple preventive health needs at once. Here’s what I coordinate in a single visit:

• Core vaccines (EEE/WEE/Tetanus, WNV, Rabies)
• Risk-based vaccines (Flu/EHV, Strangles, PHF)
• Coggins test
• Fecal egg count for parasite baseline
• Physical examination — weight, body condition score, eyes, teeth, limbs
• Dental float if needed (may require separate appointment depending on sedation logistics)
• Bloodwork for senior horses (ACTH, metabolic panel) — see our guide to Cushing’s disease in horses for why early PPID screening matters

Frequently Asked Questions About Horse Vaccinations

Have questions about your horse’s vaccination schedule, or a story about EEE or West Nile from your region? Drop a comment below — this is exactly the kind of experience-sharing that helps other horse owners make better decisions for their animals.