A vaccination protocol will be determined by the region of the area you live and the risk of exposure for your horses. For example, horses living in the south and along the coast have different exposure based on the weather than my little guys in eastern Kansas. I vaccinate against mosquito born diseases just once a year, in April. This is 3 weeks to a month prior to our last frost which means the boosted immunity should be in full force once the hot weather sets in. The shot I use is a 5 way shot- EEE, WEE, Tetanus, Flu & Rhino and also WNV. Folks along the coast and in the south will be inclined to vaccinate twice a year due to the long, hot season they have down there.
Rabies should be boosted yearly, IMO. Rabies is fatal and if your horse crosses paths w/ a rabid critter in the barn or pasture and you kiss your mini's nose because he is acting "under the weather" that morning, you are now exposed. Rabies is ugly, vaccinate against it to protect yourself and your critters.
The Strep/Strangles vaccines is recommened for horses who are hauled out and stabled w/ open populations. If you do just day shows and keep your horse at your trailer and using only your own buckets, your risk is fairly low. On the other hand, it too is a messy, nasty, time consuming illness when they get it and the cost of antibiotics to treat a horse once the abscesses blow is less than the annual shot. That's a tempting vaccine to consider if you haul out much.
The Flu/Rhino part of the above 5-way vaccine is the shortest lived part of that vaccine and to keep immunity levels up it should be reboosted every 90 days. The vaccine does not protect against all strains of Flu/Rhino but it does offer a buffer. So once again, if you are hauling out and using shared stables it would make sense to reboost it during the show season.
Potomac Horse Fever vaccines is used mostly by owners of horses along the central and northern east coast states.
The EPM vaccine is, well, doesn't look good on paper when reveiwing the protection levels it provides. A large number of horses will test positive for exposure to EPM however their own immune system holds the disease at bay. For myself, I'm waiting for a better EPM vaccine to come along before spending the $ on the only one now available.
Hope this helps some!
