While vaccination to control equine influenza (EI) in endemic areas is common practice, little is known about the use of early vaccination to eradicate the disease during an outbreak. Researchers recently examined the effect of early vaccination during an outbreak, using the 2007 EI outbreak in Australia, which had previously been free of EI, as a model.

"The Australian EI outbreak was associated with very high rates of spread in the early stages. This was a function of both an entirely naïve population, and movements and mixing of horses associated with a number of weekend recreational events prior to EI being recognized. These events were undoubtedly a key feature contributing to the size and extent of the outbreak," noted Graeme Garner, DVM, director of the animal health epidemiology program at the Department of Agriculture, Fisheries, and Forestry in Canberra, Australia.

Government agencies and the horse community implemented controls to contain the outbreak, including biosecurity measures, restricted movement, and vaccination. Approximately 140,000 horses in affected areas were vaccinated, beginning in the second month of the epidemic, as part of the nationally-coordinated EI control program.

Researchers in Australia employed a premises-level model using the epidemiological data from the 2007 EI outbreak to ascertain the role vaccination played in disease eradication and whether earlier vaccination would have made a significant impact on the epidemic.

"A detailed epidemiological model of the outbreak was constructed that took into account regional variation in disease transmission, accounted for the effects of movem