ADVANCED AGE AND IMMUNITY

There’s no truth to the notion that older horses need fewer vaccinations.

You might think your horse’s advancing age may be reason to alter his vaccination protocol, but if he’s on an appropriate program to begin with, advancing years alone don’t necessitate a change.

Likewise, there’s no truth to the notion that older horses need fewer vaccines because their immune systems have already “learned” to fight various diseases. In fact, research has shown just the opposite—a horse’s immune system may “forget” what it knows as the horse ages, a natural event called immunosenescence. In other words, more frequent vaccination might be a better plan.

Why not “pull a titer” to see if an older horse still has sufficient antibodies against a given disease? Great question.

Although previously titers were not considered a useful tool in determining a horse’s immunity to particular diseases, recent research suggest that titers can be used to determine whether a horse needs so-called “core” vaccines—those that protect against diseases that pose a threat to all horses. However, the process requires that your veterinarian send blood samples to three different labs and it will take several weeks to get results, so in most cases it is much less expensive and more sensible to simply vaccinate. Indeed, unless your horse has a history of serious reactions, the best recommendation is to vaccinate your older horse on the same schedule as younger ones in the same situation—or even slightly more often.

Titers are not yet validated for risk-based vaccines except for strangles. There is reliable research and data on titers to determine protection against Streptococcus equi so your veterinarian could, in theory, do a blood test to determine if that vaccine is needed again. But there are also considerations of efficacy and risk of side effects with the strangles vaccine, so that decision ultimately requires weighing many factors.

For now, do not consider age alone as a cause for scaling back vaccinations. It could be that, with more research, veterinarians wind up recommending a more robust vaccination schedules for older horses.