An overview of the inactivation of FMDV and the implications when residual virus is present in vaccines.

Most foot-and-mouth disease (FMD) vaccines are prepared by inactivating the virus with acetylethyleneimine or binary ethyleneimine. However, formaldehyde is still used by some manufacturers despite the well-documented evidence that inactivation with this reagent is not a linear or first-order reaction. Recent German work provides clear evidence that almost all the outbreaks in Western Europe in recent years have been caused by viruses closely related to strains which were isolated more than 20 years ago and are used for the production of vaccines. Moreover, with one exception, all the vaccines connected with the outbreaks were prepared by formaldehyde inactivation. The implications of these outbreaks are both immediate and longer term. The immediate effect is that they severely disrupt trading in meat and dairy products. The longer term effect has been the decision to abandon vaccination in Western Europe. This could have serious implications as trading with Eastern European countries will be expected to increase in the immediate future.