A stable freeze-dried smallpox vaccine made in monolayer cultures of primary rabbit kidney cells

Abstract

Smallpox vaccine was made in monolayers of primary rabbit kidney cells. The seed virus used for the production of this vaccine was the same as used for the production of calf lymph so that the vaccine contained vaccinia virus with not more than one tissue culture passage. As to other aspects this vaccine also met the international requirements for safety, potency and stability. For the lyophilization of this tissue culture smallpox vaccine a number of stabilizers routinely used for the lyophilization of several products were tested. A highly stable vaccine was obtained with 5% peptone-5% sorbitol for both the tissue culture smallpox vaccine and the calf lymph and the addition of other stabilizers did not increase the stability. With the same combination of stabilizers and lyophilized tissue culture smallpox vaccine, whether the ampoules were sealed in vacuo or in nitrogen, turned out to be more stable than lyophilized calf lymph. Cell cultures from approximately 500 rabbits were tested for adventitious agents. No cytopathic changes were observed and no viruses or other micro-organisms were isolated.