International bank for foot-and-mouth disease vaccine: stability studies with virus concentrates and vaccines prepared from them.

An international bank foot-and-mouth disease (FMD) vaccine has been established at the Pirbright Laboratory of the AFRC Institute for Animal Health. The bank is based on concentrated virus preparations stored in the gaseous phase of liquid nitrogen and is capable of producing up to 0.5 million cattle doses of each of five common strains of the virus (FMDV) for the member nations of the bank. This paper describes the initial and subsequent testing of the virus concentrates and vaccines prepared from them. There was no evidence of deterioration of the virus concentrates during liquid nitrogen storage. High levels of protection of cattle and guinea-pig were achieved when vaccines were used immediately following preparation from the recently thawed virus concentrates. In contrast, storage of vaccines at 4 degrees C for one or more months resulted in loss of potency in guinea-pigs and was attributed, in part to proteolytic enzymes in the virus concentrates.