Horse vaccination schedule: intervals, boosters, and competition rules

Last reviewed 4 August 2026

Most vaccination confusion isn't about which vaccines exist — it's about when the next one is actually due, and why your vet, your barn, and the show secretary all seem to be working from a different calendar. Here is what the published protocols say, and where they disagree.

Two questions decide the whole calendar

Before any schedule makes sense, two things need answering:

• Where does the horse live, and what circulates there? Rabies and the encephalomyelitis viruses are core recommendations in North America precisely because they are endemic here — they are not part of the routine schedule in most of Europe. Mosquito-borne disease also makes timing regional: vector season starts far earlier in Florida than in Montana.
• Does the horse meet other horses? This is what separates a backyard horse from a show horse, and it is mostly a question about influenza and herpesvirus — the two the AAEP treats as risk-based rather than core, and the two USEF checks at the gate.

The core four: annual, for every horse

The American Association of Equine Practitioners classifies four vaccines as core — recommended for every horse, every year, regardless of what it does — because the diseases are endemic, usually fatal, or a risk to people:

Rabies is the one that isn't really about the horse. It is effectively always fatal once signs appear and it is transmissible to people, which is why it stays on the core list even for a horse that never leaves its pasture — and why an unvaccinated horse with neurological signs becomes a problem for everyone who has handled it.

One detail worth knowing because it surfaces at the worst possible moment: the AAEP advises that a horse which sustains a wound or has surgery six or more months after its last tetanus booster should be revaccinated at the time of the injury. That is a question you get asked while standing in the aisle with a bleeding horse — a record you can pull up on your phone beats one filed in a drawer at home.

Risk-based: flu, herpesvirus, strangles

Influenza, equine herpesvirus (rhinopneumonitis) and strangles sit in the AAEP's risk-based category, meaning the decision depends on your horse's exposure rather than applying to everyone. In practice, if your horse ships to shows, the decision has already been made for you — see the USEF rule below.

Worth knowing about herpesvirus specifically: EHV vaccines reduce respiratory signs, viral shedding and abortion, which limits how far an outbreak spreads. But no licensed vaccine carries a label claim for preventing the neurological form (EHM). Vaccinating protects the herd more than it shields the individual, which is why biosecurity at shows — not sharing water buckets, taking temperatures, isolating on return — still matters for a fully vaccinated horse.

Show rules: the deadlines that get horses sent home

Competition rules are not clinical advice. They are eligibility conditions, they are stricter than a vet's recommendation, and they are enforced literally.

USEF (national)

Rule GR845 requires that horses over six months of age entering the grounds of a licensed competition have documentation of equine influenza and equine herpesvirus vaccination within the six months prior to entering the stables. The rule is specific about who gave the shot:

• Vet-administered: documentation from the veterinarian naming the vaccines and the dates given.
• Owner-administered: the vaccine purchase receipt, signed by the owner or agent with care, custody and control — showing vaccine name, serial number, expiration date, and date administered.

That second case is where people come unstuck. If you give your own shots, the empty bottle in the trash is not documentation; the signed receipt is. Horses not in compliance can be required to leave the grounds.

FEI (international)

Cross into FEI competition and the arithmetic changes: influenza boosters must fall within six months and 21 days of the previous dose, the primary course is two doses 21 to 92 days apart, and no vaccination may be given within seven days of the horse's arrival at the event. Booking the vet for the week of the show is the classic mistake. From 1 July 2026, influenza details must also be registered in the FEI HorseApp, not just the passport, or the athlete draws a fine.

Note the mismatch: USEF measures six months back from entering the grounds, FEI measures six months and 21 days between doses. A horse can satisfy one and not the other.

Why the calendar drifts

Almost nobody's vaccinations stay on the date they were planned. The vet reschedules, a horse is off-colour the week it was due, the second dose lands late and every subsequent date shifts with it. That is the real problem: the next due date depends on when the last dose actually happened, not on when it was supposed to.

Which is why a wall calendar written out in January quietly goes wrong by March, and why "six months from the last one" is only answerable if you know, precisely, when the last one was.

Sources

• AAEP — Equine Vaccination Guidelines (core and risk-based definitions, intervals)
• USEF — General Rules, Chapter 8 (GR845 vaccination rule)
• FEI — Vaccinations and the 2026 Veterinary Regulations
• UC Davis Center for Equine Health — EHV-1 and EHM (what EHV vaccines do and do not cover)

Guidance is revised periodically; check the current edition of any protocol before relying on it, and confirm with your vet.

In the UK? The UK version covers different vaccines and different competition rules.

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