The efficacy of inactivated oil-emulsion H9N2 avian influenza vaccine

An experimental inactivated oil-emulsion H9N2 avian influenza vaccine was formulated with 3 parts of inactivated avian influenza antigen A/Chicken/Iran/101/1998(H9N2) emulsified in 7 parts of oil adjuvant. Twelve week-old specific pathogen-free (SPF) chickens were divided into seven groups of 10 birds. Six groups were vaccinated with 1, 1/10th, 1/50th, 1/100th, 1/200th and 1/400th field dose of the experimental avian influenza vaccine (EAIV). The last group, was injected with saline and served as the control group. The mean titer in haemagglutination inhibition (HI) test (log 2) on the vaccinated groups, 21 days post-vaccination were 6.0, 4.4, 3.83, 3.3, 3.0 and 2, respectively. Prevention of virus shedding through cloaca was used as the potency test which revealed that the protective doses 50% (PD50) of full, 1/10th and 1/50th of the field dose of the experimental vaccine were 100, 100 and 96.25%, respectively. Those groups that received <1/50th dose could not prevent virus shedding. So it can be concluded that EAI vaccine could even be entirely protective and efficient in 1/10th dose and got a desirable immunity in experimental SPF chickens.