Duvaxyn® IE And IE-T Plus Claim To Cross-protect Against The Richmond/1/07 Virus

Duvaxyn® IE and IE-T Plus – the first UK Equine Influenza (EI) vaccines to be licensed to cross-protect against the Richmond/1/07 virus strain of equine influenza Elanco Companion Animal Health has announced that its Duvaxyn® IE and IE-T Plus vaccines are the first UK EI vaccines licensed for active immunisation against OIE recommended clade 1 and clade 2 equine influenza strains. The updated license is a result of a recent challenge study which demonstrated the ability of Elanco’s Duvaxyn IE-T Plus equine influenza vaccine to induce cross protection against clade 2 strain A/equi-2/Richmond/1/07 (H3N8) two weeks after two doses of the primary course¹ were given. Cross-protection was further supported by another study² measuring serum antibody response to the Richmond ’07 strain 52 weeks after the three dose primary vaccination course. The OIE (World Organisation for Animal Health) updated its equine influenza vaccine recommendations in 2010 to reflect the fact that all field strains characterised through 2008 and 2009 were of clade 1 or 2 of the Florida sub-lineage. The antigenic difference between viruses of these clades could potentially compromise the effectiveness of vaccines containing a representative of a single clade³. Anna Jackson, national veterinary manager for Elanco Companion Animal Health UK, commented: “Whilst no vaccine has been updated to match the current OIE recommendations, the results of our challenge study and subsequent licence update provide reassurance that horses vaccinated with Duvaxyn will be protected against clinical signs of disease caused by currently circulating strains of equine influenza, including those the OIE has identified as being of concern. “Further reassurance is also given with the confirmation in our study that Duvaxyn IE-T Plus elicits a cell mediated immune response, recognised to play an important role to aid in viral clearance and further enhances protection against strains circulating in the field,” ⁴ Dr Jackson added. The live virus challenge study, conducted by the Animal Health Trust, involved two groups of EIV seronegative horses. The first group, consisting of seven vaccinates, were given two doses of Duvaxyn IE-T Plus, 28 days apart, and challenged with A/equi-2/Richmond/1/07 (H3N8) virus strain 14 days after the second vaccination. The second group of unvaccinated horses was challenged at the same time. Duvaxyn IE-T Plus caused a statistically significant reduction in both clinical signs of the disease and in viral shedding. Duvaxyn IE-T Plus is the only inactivated whole virus carbomer adjuvanted equine influenza vaccine in the UK. Experts in the field of human vaccination have expressed the view that whole virus vaccines have the potential to induce a stronger and more broadly based response to circulating influenza strains than those contained in sub-unit vaccines because of the presence of the full set of virus proteins including the conserved nucleoprotein, which shows no antigenic drift, in the vaccine⁵. References:ECAH study (2011) AHT study ID C012/01ECAH study (2011) AHT study ID CO21/01OIE – World Organisation for Animal Health, Bulletin (2010), 2 pp.44-454Daly JM et al (2004) Vet Res 35: 411-423 Meeting Notes: 3rd WHO meeting on evaluation of pandemic influenza prototype vaccines in clinical trials, 15-16 February 2007, WHO, Geneva

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