Studies on an Adjuvant Newcastle Disease Vaccine

SUMMARY The preparation of an adjuvant Newcastle disease vaccine containing 25 per cent v/v embryonic fluid inactivated with beta-propiolactone and 25 per cent v/v Alhydrogel is described. The stability of the vaccine is satisfactory. While storage at room temperature causes some deterioration, the vaccine can be kept without much change in potency for at least 12 months in a refrigerator. Freeze-drying of inactivated virus for vaccine preparation does not appear to affect the potency of the vaccine. The duration of immunity conferred appears to be dependent on the dose of antigenic material administered. Provided that at least 100 fifty per cent protective doses are administered, eight-week old birds will retain immunity against homologous challenge for at least 8 months following a single administration. H. I. antibody response appears also to be related to the dose of vaccine, but is of short duration.