Vaccines are the best way to protect your horse from disease. And with some forethought and planning, you can make sure his immunization schedule provides the highest level of protection for the longest time possible. Here are four simple guidelines for ensuring that your vaccination program provides maximum protection.

1. Adapt to circumstances

When a horse’s situation changes, his vaccine needs may, too. Here are the changes in circumstances that may call for rethinking your horse’s vaccination schedule:

• Location: Certain diseases are more common in particular regions so relocating with your horse may change his risk profile. If you move your horse from Massachusetts to Georgia, for example, he’s going to be exposed to more mosquitoes and needs more frequent vaccination against the diseases they carry. A move to a location near a river or body of water might increase his risk of Potomac horse fever. It’s wise to take precautions even if you’ll only be making a temporary move; if you’re taking part in a weeklong riding clinic or camping trip, for example, call an equine veterinarian at that location to find out which vaccines are recommended there.

• Lifestyle: Horses who travel to events such as shows, clinics and community trail rides are more likely to interact with others whose vaccination histories you won’t know. That means they are more likely to be exposed to communicable diseases than horses who hang out with only their regular herd. If your horse’s schedule becomes busier, talk to your veterinarian about expanding his vaccination regimen. Likewise, if he’s scaling back on his activities, you may be able to reduce the number of vaccines he receives.

• Social life: Even if your horse doesn’t travel much, his herdmates might. Horses returning to the farm can bring pathogens with them and infect others who never left. If your horse’s companions need a stepped-up vaccination program due to increased activity, so does he. Consider your neighbor’s horses, also. Many pathogens are airborne or travel via insect. If your horses can get within 50 feet of your neighbor’s horses, it’s smart to ask whether they travel, and vaccinate your horses accordingly.

2. Consider your horse’s health and activities

Because vaccines work by triggering an immune response, a horse’s overall health could affect their efficacy. That’s why it’s important to consider illnesses and stressful activities when scheduling his vaccinations.

If your horse has been sick in the last week or so, it may make sense to put off vaccinations until he’s feeling better. This also goes for health incidents that aren’t pathogen-related, like colic or choke. The reason for waiting is to make sure his immune system will be at full strength when responding to the vaccine. You need only wait a few days, however, not weeks or months. The flip side of this guideline is that you may not want to vaccinate your horse just prior to a stressful event, such as a long trailer ride to a competition. The stress may keep his immune system from responding fully to the vaccine. Give him a day or two to recover before immunizing him.

Even if physical stress doesn’t interfere with immune function, there’s still good reason to avoid vaccinating a horse just prior to physical activity. Some horses develop injection site soreness or may run a slight fever in response to certain vaccines. These aren’t adverse reactions—in fact, they are indications that the immune system is responding appropriately—but they can leave the horse feeling a little off for a day or two. He’d likely appreciate being able to take it easy for a while.

On the other hand, there’s no reason to forgo or scale back on vaccinations for horses with chronic health conditions that are being managed and monitored. In fact, these horses may require even more vigilance. For instance, research into the effects of immunization on horses with PPID is still ongoing, but the recommendation is likely to be for a regular vaccination schedule with more frequent doses for these horses.

The only other reason to revisit a vaccination decision is after a horse has had a serious reaction to a specific formulation. Reactions are rare, but the few that do occur are usually associated with the vaccine’s adjuvant, the substance added to boost the immune response. Adjuvants are tested for safety and most horses have no problems with any of them, but a few vaccine formulations contain mercury or other substances that can cause a reaction in sensitive animals. If your horse has a serious reaction to a particular vaccine, look for a different formulation that protects against the same disease—chances are it will not cause a problem.

3. Make a schedule and do boosters when needed

Vaccines work by “teaching” a horse’s immune system to recognize and fight a foreign invader. When planning your vaccination schedule, you’ll want to leave enough time for that lesson, which can take days or even weeks, to occur. Consider, for example, vaccination against insect-borne encephalitis diseases, such as EEE, WEE or WNV. You’ll want to have the immunization done well before the bugs are buzzing. Waiting until the weather warms is too late to confer complete protection—although when this can’t be avoided, better to vaccinate late than not at all.

When a horse is first vaccinated against a disease, he may need to undergo a series of injections as opposed to a single shot. These injections are delivered weeks apart, so determine with your veterinarian when you’ll want full protection and work backward from there when scheduling appointments. Work out the entire timeline, set the appointments and then keep them. A single shot in a series offers some protection to a naïve horse but not the same as he would get from completing the series. Even after a horse is up to date on his vaccines, there may be times when an additional vaccination makes sense because of a new health risk. A horse with an open wound, for instance, will likely benefit from another tetanus shot if it’s been more than six months since his last booster. A veterinarian will immediately revaccinate a horse that may have been exposed to the rabies virus, regardless of how recent his last rabies shot was given.

4. Keep an eye on the news

West Nile virus (WNV) was once a foreign disease. No one in the United States had to worry about it or vaccinate against it. Now we do. After WNV appeared on the East Coast, it raced across the country. Veterinarians and owners had to educate themselves quickly and, once a vaccine was available, determine which horses needed protection. This scenario is likely to play out again at some point with another disease, and you can be prepared by being on the lookout for reports of emerging diseases.

In addition to paying attention to traditional news outlets and equine-specific publications, you can sign up for alerts from the Equine Disease Communication Center, which provides real-time information about disease outbreaks across the country.

Keep in mind that it’s not just new diseases that may suddenly appear in your area. The changing climate has led to an expansion of the range of diseases that used to be geographically limited. We know that Lyme disease is spreading to areas where it never used to be endemic—there has been research specifically looking at that—and the same thing is undoubtedly happening with other diseases. Do a lot of reading, talk to your veterinarian and stay on top of these things so you’ll be ready for new disease threats.

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