[The effectiveness of foot-and-mouth disease vaccines in Switzerland. I. Screening tests and herd immunity].

Protection of the Swiss national cattle herd against foot-and mouth disease is attempted by annual vaccination with inactivated trivalent (O, A, C) vaccines. With the serotype A5 as an example, this paper demonstrates the procedure of potency testing. Serological data obtained with two vaccines in primovaccinated feeder bulls showed that neutralizing antibodies developed within 7 to 14 days post vaccination. There was no statistically significant difference in the anti-serotype antibody titers induced by each of the vaccines; differences were seen between anti-O serotype and anti-A serotype antibody titers, regardless of which vaccine was used. Epidemiological analyses with about 3000 cattle demonstrated that single-vaccinated, and to a lesser degree twice-vaccinated, animals often had short lived immunity; that is, the antibody titers waned within a few months. In contrast, the majority of thrice and multiple vaccinated animals maintained relatively high antibody titers throughout the twelve month period of observation.