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Hypersensitivity Reactions
in Cattle Following Immunisation
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Adverse reactions are occasionally observed in vaccinated animals. These are almost invariably attributable to the older, impure form of FMD vaccine which is still manufactured in some parts of the world. Adverse reactions are essentially of two types:
The first is a simple local or systemic reaction to components of the vaccine such as saponin, residual inactivant and antigens from the production cells. This is most pronounced with crude or partially purified vaccines and may cause a significant, albeit transient, drop in the milk production of dairy cattle. This drop is negligible when purified antigens are used for vaccine production.
The second is an allergic response, either of an immediate or delayed-type hypersensitivity or both. It is not uncommon for animals to die of anaphylactic shock following the triggering, by injection of vaccine, of a hypersensitivity state not previously known to the owner of the animal.
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