THIS LIVE VIRUS VACCINE IS PREPARED FROM THE ATTENUATED STRAIN;H120 . THE VIRUS IS PROPAGATED IN EMBRYONATED EGGS OBTAINED FROM;DISEASE-FREE FOWLS.IT IS ISSUED IN FREEZE-DRIED FORM BUT THE FINAL;VACCINE IS TESTED FOR SAFETY AND EFFICACY BEFORE RELEASE. THE;TEMPERATIRE STABILITY OF THE VACCINE IS ALSO DETERMINED AND THE;MINIMM STANDARD REQUIRES AT LEASE 10^3 VIRUS PARTICLES DOSE AFTER;EXPOSURE TO 37℃ FOR ONE WEEK.