Potential for polyvalent infectious bronchitis vaccines.

Numerous antigenic types and subtypes of infectious bronchitis virus (IBV) have been isolated and characterized from field epornitics of infectious bronchitis (IB). Thus obvious failures in obtaining the necessary protection from vaccination have been documented and they underscore the urgent need for vaccines which stimulate a broader spectrum of protection from heterologous IBV challenge than is presently obtained. If polyvalent IB vaccines are to be employed, assurance must be provided that variant IBV serotypes are not indiscriminately spread throughout the country or globe. Furthermore, possible interference, alteration, and reduction in immune response with the component antigens should be critically evaluated. Differences and comparative levels of postvaccinal respiratory signs with the different antigens, used singly and in combination, should be determined. As an alternative to polyvalent IB vaccines, certain Massachusetts-type strains, e.g., a Holland isolate IBV, at different passage levels in the authors' laboratory, have induced heterologous and homologous protection to some serotypes causing vexing field problems. Advantages are present in using a single antigenic type IB vaccine, if it is safe and effective, when compared to polyvalent vaccines. The absence of a serologic relationship to the results of immunity challenge is frequent with IBV isolates, which emphasizes that challenge results are considerably more important. In some IB problems, on a local or regional basis, autogenous vaccines may be indicated. Because of the multiplicity of IBV serotypes, however, it is doubtful that completely effective and safe IB vaccines will be forthcoming in the near future to satisfy the diverse needs of a dynamic poultry industry.