Development and performance of inactivated vaccines against foot and mouth disease.

The historical background of foot and mouth disease (FMD) vaccine production is briefly described. Improvements achieved through the use of monolayer and suspension cultures are outlined. Elements that are crucial in the production of modern vaccines are discussed, such as inactivation of viral antigen, successive concentration and purification of the antigen and the final formulation of the vaccine. Storage of concentrated antigen at ultra-low temperatures creates greater flexibility for the producer and has also enabled national and international organisations to establish vaccine banks. The purification of FMD viral antigens, including the removal of non-structural proteins (NSPs), enables the immune responses of vaccinated animals to be distinguished from the responses of animals infected with live FMD virus. Consequently, the combined use of purified vaccine and tests for the detection of antibodies against NSPs essentially provides a marker system to distinguish between vaccinated animals that subsequently become infected and those that have not. Bearing in mind the good record of modern vaccines in the control of outbreaks and the possibility of screening vaccinated herds for carriers, the author proposes that the OIE reconsider the differences between the requirements for regaining export status following the use of stamping-out as opposed to vaccination in outbreak situations.