Vaccinating the older horse... is there an age when you just don't?

[JB]

@Libby2563

Interesting that the AAEP link says: “If Potomac Horse Fever has been confirmed on a farm or in a particular geographic area, it is likely that additional cases will occur in future years. Foals appear to have a low risk of contracting the disease. Vaccination against this disease has been questioned because field evidence of benefit is lacking. Proposed explanations for this include lack of seroconversion and multiple field strains whereas only one strain is present in available vaccines.” Most practices in this area consider that a core vaccine.

The PHF vaccine is one of the least effective ones that are still effective enough to keep FDA approval. IIRC its efficacy is about 75%. But, the reason for that reduced efficacy isn’t the same as, say, for the EPM vaccine. PHF has a great many strains, and mutates frequently. The vaccine is only for one of those (as stated)

However, vaccinating for it does help immensely if/when a horse does contract it, in helping mitigate symptoms.

I have friends in the Ontario area where PHF is pretty common. Vaccinated horses still get it, but rarely die. Unvaccinated horses almost always die, and when they don’t, it’s due to touch and go $$$ treatment.