Avian infl uenza (AI) occurs worldwide and causes tremendous economic losses. Th e disease is characterised by respiratory signs, depression, and reduced food and water intake. In the present study, an oil-based vaccine was prepared by using by using Montanide ISA 70 MVG, was prepared and the duration of immunity checked at diff erent time intervals. For this purpose, the cumulative mean titre (CMT) was calculated aft er employing haemagglutination inhibition test in 50 pullets at day zero

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... e vaccination and then inoculated 0.3 mL of emulsifi ed vaccine subcutaneously in 40 birds while 10 birds were kept non-vaccinated as a control group throughout the experiment. On day 21, a booster dose of 0.5 mL emulsifi ed AI vaccine was injected into the vaccinated birds that produced highest CMT at day 63 and maintained the protective antibody titre on day 84, 105, 126, 152, 182, and 228 in layers. Th e study showed that a booster dose at day 21 produced a high protective AI antibody titre in birds that minimises the stress of repeated shots of aqueous vaccine.