RESUMEN
The GDR in 1977 had been the first country to introduce a laboratory method for potency testing of FMD vaccines on the basis of secured correlations between titres of virus-neutralising serum antibodies of immunised cattle, on the one hand, and their probit-transformed protection against FMD, on the other. This is now the only state-registered method for potency testing. The method has ever since worked well all over the place. An evaluation of results obtained between 1982 and 1988 revealed seasonal variations of anti-FMD immunogenesis in cattle. FMD immunisations from February to July proved more effective than those performed in the rest of the year, in that higher antibody titres were built up within 14 days from vaccination. These results were confirmed by rates of protection of cattle recorded from direct potency testing of immunised animals, between 1969 and 1977.