a1 Department of Infectious Diseases, Animal Health Trust, P.O. Box 5, Newmarket, UK
a2 Solvay Duphar B.V., P.O. Box 900, 1380 DA, Weesp, Holland
Equine influenza vaccines containing inactivated whole virus and Carbomer adjuvant stimulated higher levels and longer lasting antibody to haemagglutinin in ponies than vaccines of equivalent antigenic content containing aluminium phosphate adjuvants. Five months after the third dose of vaccine containing Carbomer adjuvant, ponies were protected against clinical disease induced by an aerosol of virulent influenza virus (A/equine/Newmarket/79, H3N8). In contrast ponies which received vaccine containing aluminium phosphate adjuvant were susceptible to infection and disease. There was an inverse correlation between prechallenge levels of antibody detected by single radial haemolysis (SRH) and duration of virus excretion, pyrexia and coughing. All ponies with antibody levels equivalent to SRH zones of ≥ 154 mm2 were protected against infection and all those with levels ≤ 85 mm2 were protected from disease.
(Accepted November 01 1993)