Potency of live Newcastle disease vaccines

A comparison was made of the potency of live lentogenic Newcastle disease vaccines using a multipoint challenge assay. In general, La Sota vaccines gave better protection than B1 vaccines and both were superior to products made from the Ulster 2C strain. However, variation was found within products prepared from the same strains, depending on their source. Two novel types of vaccine derived from the conventional B1 or La Sota strains were as protective as La Sota vaccines and a third gave protection similar to that of B1 vaccines.