Each seed virus used for vaccine manufacture shall be prepared from an acceptable strain in monkey kidney cell cultures, derived from animals…or in a cell culture of a type determined to be suitable by the Director…The seed virus used in vaccine manufactures shall be demonstrated to be free of extraneous microbial agents except for the unavoidable bacteriophage.
Some live human virus vaccines have been shown to contain bacterial viruses. Why would there be ‘unavoidable bacteriophage’ in seed virus and vaccines? If you know the answer, post it in the comments section, and I’ll explain fully tomorrow. I’ll also tell you why this has been an all-poliovirus week at virology blog.