A three-year evaluation of four commercial equine influenza vaccines in ponies maintained in isolation.

This study examines the effectiveness of four commercial equine influenza vaccines given to ponies in isolation over three years. The research indicates an initial low response, with improved results on second and subsequent annual revaccinations.

Methods and Research Setup

• The researchers carried out the study over a period of 40 months with ponies kept in isolation for the duration of the experiment.
• The ponies involved were vaccinated and revaccinated with four different commercial equine influenza vaccines.

Initial Vaccine Response

• According to the researchers, there was little to no detectable HI (Hemagglutination inhibition) antibody response after the first inoculation.
• This means that the first dose of the vaccine did not significantly stimulate the immune system to produce antibodies to fight against the influenza virus.

Subsequent Vaccine Responses

• Upon second and subsequent annual revaccinations, an improved immune response was observed.
• There was a peak in HI antibody levels between 7 to 14 days following these revaccinations.
• However, these antibody titres fell sharply within the first month after vaccination, and then decreased at a slower rate thereafter.

Factors Influencing HI Antibody Levels

• The decline in HI antibody levels appeared to be more closely tied to the initial titre achieved and the time elapsed since vaccination, rather than the specific composition of the vaccine itself.
• In other words, the initial immune response to the vaccine and the time after vaccination appeared to play a more significant role in the rate of antibody level decline than the particular ingredients or formulation of the influenza vaccine.

Comparisons between First and Second Annual Revaccinations

• The immune response produced by a first annual revaccination was found to be superior to that produced by a second annual revaccination.
• Thus, time elapsed since the first revaccination plays a vital role in the immune response of the ponies.

Requirement of Ether-Treated Antigens

• Ether-treated antigens were needed to identify both primary and secondary immune responses to the equine-2-component of vaccines.
• This suggests that a special type of antigen processing (ether treatment) was necessary to detect the immune response specifically to the equine-2-component part of the vaccine.