INFLUENZA IMMUNITY IN HORSE

Antibodies anti-equine influenza virues (H7N7 and H3N8) were searched in sera from 433 horses by hemagglutination inhibition tests. Twenty-n ine per cent of 79 vaccinated animals showed antibodies against one an d/or both viral strains tested (A/equi/1/Prague 56 (H7N7) and A/equi/2 /Miami 63 (H3N8)), and only 13 per cent had titers that may be conside red as protective (greater than or equal to 40). In 354 unvaccinated a nimals, these percents were respectively of 10 and 4. Seventeen horses were followed over a six mouths period after a booster injection of a bivalent influenza vaccine. Sera were sampled at days 0, 7, 15, 30 an d 180 after the vaccine administration. The results show an irregular and faint booster effect and revael the limitis of this kind of vaccin ation.