Evaluation of the thermal stability of live-attenuated Rubella vaccine (Takahashi strain) formulated and lyophilized in different stabilizers

Live attenuated viral vaccines are difficult to handle and often sensitive to temperature. The viral titer may drop during the processing and storing stage, especially at high temperatures. Using live attenuated viral vaccines successfully depends on keeping the sufficient potency required - for an immune response. Although freeze-drying makes the vaccine more stable, in the absence of appropriate stabilizer the process may affect the structure and viability of the viruses. Therefore, the formulation of vaccine by means of an appropriate stabilizer plays a crucial role in the stability of viral structure and potency of the vaccine. This study aimed to evaluate the effect of two new stabilizers, including a Trehalose-based stabilizer (T) and a stabilizer containing sucrose, human serum albumin and sorbitol (S) on the thermal stability of lyophilized live-attenuated Rubella virus (Takahashi strain). Two Rubella vaccines were formulated using different stabilizers and were lyophilized. The potency of produced vaccines was investigated using accelerated stability test. To determine the pattern of thermal stability of reconstituted vaccines in 24 h, incubating at three different temperatures and continuous sampling was also included in this study. The viral titer was calculated by TCID50 method. The regression analysis revealed that T vaccine found the sufficient stability compared to commercial Rubella vaccine containing a gelatin-based (G) stabilizer.