For active immunisation of chickens and ducks against avian influenza type A, subtype H7N1. Efficacy has been evaluated on the basis of preliminary results in chickens and ringed teals. In chickens, reduction of clinical signs, mortality, excretion and transmission of virus after challenge were shown by two weeks after a single dose vaccination. In ducks, reduction of excretion and transmission of virus after challenge were shown by two weeks after a single dose vaccination. Although it has not been investigated with this particular AI vaccine strain, studies performed with other strains show that protective levels of serum antibody titres would be expected to persist in chickens for at least 12 months after administration of two doses of vaccine. The duration of immunity in ducks is unknown.