Abstract
This study is the second of four transmission experiments assessing long-term protection provided by vaccination of laying hens under field conditions against highly pathogenic avian influenza (HPAI) H5N1 (clade 2.3.4.4b). The primary objective is to evaluate whether vaccination reduces virus transmission (R<1). Previously, vaccination with VECTORMUNE® AI or VAXXITEK HVT+IBD+H5 provided protection at 8 weeks post-vaccination. This study investigates protection at 24 weeks, including the effects of a Volvac® B.E.S.T. AI+ND booster at 12 weeks after VAXXITEK HVT+IBD+H5 vaccination. Chickens reared under field conditions were transported to high-containment facilities at peak egg production and challenged with HPAI H5N1. Four groups were studied: (1) non-vaccinated controls, (2) VECTORMUNE® AI-vaccinated, (3) VAXXITEK HVT+IBD+H5-vaccinated, and (4) VAXXITEK HVT+IBD+H5 plus booster. All control chickens were infected (R=15.4). Transmission was lower in vaccinated groups (VECTORMUNE® AI: R=1.0 or 1.9; VAXXITEK HVT+IBD+H5: R=7.9 or 2.8), with only the booster group achieving R<1 (R=0.6 or 0.3). Mortality was 100% in controls but reduced to 10% in groups 2 and 3, with none in the booster group. Virus shedding was lower in vaccinated chickens. All vaccinated groups developed antibodies, and VECTORMUNE® AI showed significant T-cell proliferation and T-cell activation at 7 dpi. Vaccination reduced transmission, mortality, and virus shedding. Only the booster group achieved R<1, though confidence intervals were broad. Further analysis of field data and additional transmission studies are needed to confirm vaccine effectiveness over the full production cycle and its potential to prevent sustained transmission.
Co-Author(s)
K.M. Bouwman1, C.A. Jansen2, M.C.M. de Jong2, M. Augustijn-Schretlen3, T. Fabri3, M.K. de Wit3, J.A. Stegeman4, F.C. Velkers4, J.J. de Wit3,4, N. Beerens1, E.A. Germeraad1, J.L. Gonzales1 1 Wageningen Bioveterinary Research, Lelystad 2 Wageningen University & Research, Wageningen 3 Royal GD, Deventer 4 Utrecht University, Utrecht
Abstract Category
Late Breaking