Vaccination against Newcastle disease: efficacy of an oil emulsion vaccine.

Vaccination using injectable Newcastle vaccine (inactivated) oil emulsion at 21 days of age stimulated high and persistent H.I. antibody levels. Vaccine prepared on an industrial scale contained not less then 100 PD50 in 0.5 ml. High levels of maternal antibodies had a negative influence on vaccination of chickens when carried out during the first 3 weeks of age, but not when performed later. Vaccine stored in a refrigerator (at 8 degrees to 4 degrees C) or at room temperature (20 degrees C) retained its potency for at least 1 year.