The protective efficacy of a subunit
avian influenza virus H5
vaccine based on recombinant baculovirus expressed H5 haemagglutinin
antigen and an inactivated H5N2
avian influenza vaccine combined with a
marker antigen (
tetanus toxoid) was compared with commercially available inactivated H5N2
avian influenza vaccine in young ducks. Antibody responses, morbidity, mortality, and virus shedding were evaluated after challenge with a Vietnamese clade 1 H5N1 HPAI virus [A/VN/1203/04 (H5N1)] that was known to cause a high mortality rate in ducks. All three
vaccines, administered with water-in-oil adjuvant, provided significant protection and dramatically reduced the duration and titer of virus shedding in the vaccinated challenged ducks compared with unvaccinated controls. The H5
subunit vaccine was shown to provide equivalent protection to the other two
vaccines despite the H5 antibody responses in subunit vaccinated ducks being significantly lower prior to challenge. Ducks vaccinated with the H5N2
marker vaccine consistently produced antitetanus
toxoid antibody. The two novel
vaccines have attributes that would enhance H5N1
avian influenza surveillance and control by vaccination in small scale and village poultry systems.