Which of the following is true about the Eastern/Western Equine Encephalitis vaccine?

The Eastern/Western Equine Encephalitis vaccine is indeed administered once annually after an initial series of doses. This reflects the vaccination protocol that ensures horses maintain adequate immunity against these viruses, which can cause serious neurological diseases.

Initially, horses will receive a series of doses to build up their immunological defense against equine encephalitis, and after this initial vaccination process, a single booster dose is sufficient each year to sustain immunity. This annual schedule is based on the time it takes for immunity to wane, ensuring that horses remain protected throughout the year, especially during peak seasons when the risk of exposure to the viruses is higher.

In contrast, the other choices suggest different vaccination protocols that do not align with common veterinary practices. Some may imply a frequency that is either too frequent or too infrequent for effective immunization. Knowing the proper vaccination schedule is essential for horse owners to ensure their animals are protected against potentially fatal diseases like Eastern and Western Equine Encephalitis.