The proposed international standard for infectious bronchitis vaccine (live).

An H-120 strain of infectious bronchitis virus was prepared in a form suitable to serve as an international standard for Infectious Bronchitis Vaccine (live). Accelerated degradation studies carried out on this vaccine showed it to be of suitable stability to serve as a standard. Results from a collaborative assay involving ten laboratories demonstrated that the proposed standard reduced the variation in virus titrations both within and between laboratories. This assay also showed that firstly the proposed standard could be used as a reference vaccine for the different safety tests described by the collaborating laboratories, and secondly as a reference vaccine in the different potency tests.