Stability of purified Vero cell-derived inactivated Japanese Encephalitis vaccines under various conditions

Abstract

The stability of three batches of purified Vero cell-derived, inactivated Japanese encephalitis vaccines was evaluated under various conditions. Vaccine products were stored separately at 2 to 8 ℃ and 37 ℃. At various times, vaccines samples were taken and evaluated for appearance, pH, residual aluminum, titer, and the results were compared with corresponding data of release tests. All three batches of vaccine products were conforming to release test standards, with residual host DNA being less than 100pg/dose, residual protein being 23.5ng/ml, and residual bovine albumin being 8.9ng/dose, respectively. During storage under various conditions, no abnormal appearance was observed; pH was slightly increased and residual aluminum level was decreased, both of which were within acceptable range of standards. The titers of vaccine products were determined by Plaque Reduction Neutralization Test (PRNT). Three batches of vaccine products that were stored at 37±1℃ for 4 weeks were found to maintain titers of above 95%. When stored for 12 weeks, there was an apparent decrease of titer (maintained at 78.6% to 81.5%). Except batch 20081101 showed T values less than standard, other two batches were still qualified. Three batches of vaccine products that were stored at 2~8℃ for 36 months were found to maintain titer of 85.4% ~86.7%, with potency T values above that of reference product. At major time points of this storage condition, sterility, abnormal toxicity, and endotoxin level were all conforming to standards. This study indicates that these vaccine products have excellent stability within specific duration of storage under various conditions.