An evaluation of the stability of Brucella abortus strain 19 reduced dosage lyophilized vaccines produced by different methods.

Replicate lots of multiple dose lyophilized Brucella abortus strain 19 vaccine were prepared having four different cell concentrations and four different fill volumes. In addition, two different size vials utilizing cells prepared by three different methods were studied. This vaccine was maintained at four different storage temperatures and the viability determined periodically. There was no appreciable loss in viability that could be attributed to the method of cell preparation; however, marked differences in viability were associated with cell concentration and/or prelyophilization fill volume and the two vial sized. The optimal prelyophilization cell suspension contained 25 to 35 X 10(9) viable Brucella 1 per ml. The better lyophilization vials had dimensions which minimized the surface to volume ratio of the postlyophilization pellet. Based on these studies it was concluded that production of large volumes of reduced dosage lyophilized vaccine is feasible and that the vaccine produced will meet specifications currently being implemented in the United States. These specification will require that each two ml dose of vaccine contain between three and ten X 10(9) viable organisms of B. abortus strain 19.