Vaccines prevent clinical disease but often allow some virus excretion. It is therefore necessary to vaccinate most of the population at risk. The goal is to reduce the amount of circulating virus until no new infections occur. The vaccination programme can then cease eg SFV and Aujesky's virus of pigs in some countries, but infected stock must then be excluded.

Any governmental decision to vaccinate has to be taken with care 1) if the disease is exotic and clinical signs need to be recognised immediately (e.g. FMDV) and 2) if antigenic variation can nullify vaccination (e.g. FMDV and avian influenza).

New vaccines must be licensed and the EU /UK licensing procedures require animal experiments in lab or target species to show protection.