[The effectiveness of foot-and-mouth disease vaccines in Switzerland. II. Stability problems].

One of the vaccines that were used in 1988 to immunize the Swiss national cattle population against foot-and mouth disease (FMD) was apparently not stable. Data, provided by the manufacturer, indicated a high initial antigenic content for serotype O. Protection experiments at the end of the vaccination campaign, however, indicated a substantial loss of serotype O antigen in the vaccine. Serological data, obtained during the campaign indicated that only 12% of the primovaccinated animals and 63% of previously vaccinated animals received an amount of FMD viral antigen sufficient to induce protective immunity. The primovaccinated animals were revaccinated in fall 1988 with a new batch provided by the same manufacturer. The new vaccine induced high titers of neutralizing antibodies in primo- and an anamnestic response in revaccinated cattle.