Effect of storage temperatures on opacity and total nitrogen content of cholera vaccine

Fluid cholera vaccine was examined for its stability at 4-8 degrees C, 20-25 degrees C and 37 degrees C with regard to the number of organisms present and the total nitrogen content. Ten batches of fluid cholera vaccine manufactured at the Central Research Institute, Kasauli, India were taken for the study. The number of organisms was determined at weekly intervals for the first month and at monthly intervals for the next 11 months. The percentage loss in the number of organisms after one year averaged 6.5 at 4-8 degrees C, 20.6 at 20-25 degrees C and 21.5 at 37 degrees C. The maximum loss in number of organisms took place during the first six months at these temperatures, in the following six months the number of organisms remained almost constant even at 37 degrees C. The total nitrogen content of the vaccine remained virtually unaltered during the same period. From this study it was concluded that the number of organisms and the total nitrogen content does not reflect the antigenicity nor potency of the vaccine.