The thermostability of rabies virus was studied by subjecting the ERA strain produced in Vero cells to accelerated aging (7 days at 37°C) in the presence of stabilizers.

The analysis of the obtained results by in vivo titration method (inoculation of rabies virus to young mice) revealed that the rabies virus ERA/Vero keeps well without stabilizers at -20°C or -70°C, fairly well to +4°C, but it is sensitive to temperatures above 25°C and 37°C. The rabies virus ERA/Vero stored at 37°C for 7 days is found with an acceptable title. Apart from the PBS and the saccharose at 2% carried by the Enders buffer, all the other media used in this study: Enders buffer, sorbitol at 1% carried by Enders buffer, sorbitol at 4% carried by the PBS, sorbitol at 4% carried by distilled water, have a stabilizing effect on the rabies virus ERA/Vero after 7 days of incubation at 37°C. The best stabilizing effect on the rabies virus is obtained with the sorbitol at 4% carried by the PBS. The saccharose was ineffective; its use to a concentration at 2% carried by the Enders buffer gave a negative effect on rabies virus. The sorbitol solution at 4% carried by the PBS can be an ideal formulation, adequate and economical to be incorporated in vaccine preparations, in order to reach the production of a rabies thermostable vaccine.