The standardization of vaccines: a discussion

Many changes have been made in the World Health Organization's (WHO) requirements for the production and control of both the killed and live (oral) poliovirus vaccines since their initial formulations in 1959 and 1962, respectively. The major changes in the production of killed vaccine concern the cell substrates used from primary tissue to passaged primary tissue or even a continuous cell line such as Vero. It has been shown also that there is no longer the necessity to test for residual infectious virus by the inoculation of monkeys, since cell cultures are much more sensitive for this purpose. For the live vaccine, a more uniform test for the titration of virus content has been introduced. Furthermore, international agreement on the details of the test for neurovirulence in monkeys has been reached. The expression of the immunogen of poliovirus in eukaryotic cells has been achieved, but whether it becomes a commercial proposition replacing one or both of our present vaccines remains to be seen.