Bacteriophages and endotoxin in licensed live-virus vaccines

In confirmation of recent reports, coliphages were found in seven of 19 unselected samples of the currently licensed live-virus vaccines. Coliphages and pseudomonas phage were found in 11 and 14, respectively, of the 20 bovine sera commonly used in the cell culture phase of virus vaccine production. The same lots of vaccine and serum were examined by the limulus assay for endotoxin, another product of bacterial contamination. Eighteen of 20 sera had detectable endotoxin-like activity. Our preliminary results suggest that endotoxin activity may serve as a sensitive indicator of residual products of previous bacterial contamination, including bacteriophages.