Horse Vaccination Schedule: Core and Risk-Based Vaccines Explained

Core vaccines are the ones recommended for nearly all horses because they protect against severe, widely relevant, or public-health-important diseases. In current AAEP guidance for U.S. horses, those core vaccines are rabies, tetanus, West Nile virus, and Eastern/Western equine encephalomyelitis (EEE/WEE).

For most adult horses with a known vaccine history, these are typically boosted once yearly. Timing matters. Mosquito-borne vaccines such as West Nile virus and EEE/WEE are usually given before vector season, and broodmares are commonly boosted 4 to 6 weeks before foaling. Horses in long mosquito seasons, younger horses under 5 years, or some older horses may need more frequent review with your vet.

Risk-based vaccines are chosen after looking at your horse’s lifestyle and local disease exposure. Common examples include equine influenza, EHV-1/EHV-4 (rhinopneumonitis), strangles, Potomac horse fever, botulism, and rotavirus for broodmares on affected farms.

These vaccines are not optional in the sense of being unimportant. They are situation-dependent. A horse that trailers to shows, lives in a busy boarding barn, breeds, or lives near freshwater in a Potomac horse fever area may benefit from a very different plan than a retired horse with minimal outside contact.

For a previously vaccinated adult horse, a practical baseline is an annual wellness vaccine visit that includes the core vaccines. Many horses also receive influenza and EHV boosters every 6 months if they travel, compete, breed, or have frequent contact with outside horses. In lower-risk horses, those respiratory vaccines may be given annually instead.

Adult horses with unknown history often need to restart selected series rather than receiving a single booster. For example, AAEP adult guidance lists a 2-dose primary series for previously unvaccinated adult horses for several core vaccines such as tetanus, West Nile virus, and EEE/WEE, followed by annual revaccination.

Foal schedules are more complicated because maternal antibodies can block an early vaccine response. In general, foals from vaccinated mares often start some vaccines later than foals from unvaccinated mares. Merck notes, for example, that foals from vaccinated mares may receive influenza at 9, 10, and 12 months, while foals from unvaccinated mares may start earlier.

Broodmares are often boosted before foaling to improve antibody transfer in colostrum. AAEP adult guidance lists rabies, tetanus, West Nile virus, and EEE/WEE boosters 4 to 6 weeks prepartum for previously vaccinated mares. For EHV abortion prevention, broodmares commonly receive a 3-dose series at 5, 7, and 9 months of gestation with a product labeled for that use.

AAEP guidance supports more frequent boosters in some higher-risk settings. Equine influenza may be boosted every 6 months in horses with ongoing exposure, such as show, race, or sale horses. EHV-1/EHV-4 may also be considered on a 6-month interval in younger horses, breeding farms, horses in contact with pregnant mares, and high-risk performance horses.

For Potomac horse fever, AAEP adult guidance lists semi-annual to annual boosters, with even 3- to 4-month revaccination considered in endemic areas when disease risk is high. Botulism is risk-based and especially relevant in endemic regions such as Kentucky and parts of the Mid-Atlantic, or in horses fed high-risk forage.

Costs vary by region, farm-call structure, and how many horses are seen on the same visit. In many U.S. practices in 2025-2026, a single core vaccine often runs about $20 to $45, while risk-based vaccines may run $25 to $60 each depending on product and route. A farm call may add $40 to $120+, and a wellness exam may add $50 to $110.

That means a straightforward annual core visit for one adult horse may land around $150 to $300, while a horse needing core vaccines plus influenza, EHV, and strangles may be closer to $250 to $450 or more. Ask your vet for a written prevention estimate, especially if your horse is a broodmare, foal, or frequent traveler.

Call your vet if your horse is overdue, has an unknown vaccine history, is pregnant, is about to travel, or had a prior vaccine reaction. Also check in before adding a new horse to the property or before show season starts. Vaccine timing can affect both protection and event-entry requirements.

After vaccination, mild soreness or a small temporary swelling can happen. But if your horse develops hives, facial swelling, trouble breathing, collapse, severe lethargy, or a high fever, see your vet immediately. AAEP notes that severe reactions, including anaphylaxis, are possible with any vaccine, which is one reason vaccines are best given by or under the direct supervision of your vet.