Experience with the active immunization method for determining the potency of typhoid vaccine

ABSTRACT

The study was done to gain experience with the active immunization method for vaccine potency testing. It also determined the relative potency of locally prepared vaccines compared with foreign prepared vaccinesWhite Swiss mice equally distributed as to sex were used as control and test groups. Granular mucin type 1201-w, strain of Salmonella typhosa, and three vaccines (vaccines A,B, and C) were used. The procedure used was the mucin technique of RakeThe LD50 dose was found to be 0.5 ml of a dilution of 10-5-752. It was felt necessary to enhance virulence of the organism, thus another determination was done after two passages. Results of potency determination showed that vaccine A gave a protection to approximately 1,500 LD50 dose. However, vaccines B and C failed to protect immunized animals against the minimal number of LD50 doses measurable in the range of the tests conductedFurther studies involving V antigen are deemed needed to supplement this initial experience