Replacement of animals in manufacture and control of vaccines.

The first vaccines were obtained from animals infected with the vaccine viruses. Bacterial vaccines were derived from culture media prepared from animal tissues. In some cases the principles of manufacture remained unchanged for more than a century, the methods only were refined. Animal cell culture was not introduced into vaccine production until the second half of of this century. After more than 25 years the search for non-animal substrates and their improvement still goes on. Control of vaccines lagged behind this progress. After a period of no control for the early vaccines, animal tests enabled immunologists to measure safety and potency, thus eliminating the disasters attributable to unsafe products or failures in protection. In vitro methods of control led to a better understanding of the immunology of vaccines. Replacement of animals in manufacture is now to be paralleled by their replacement in control. This will require courage from both the manufacturer and the controller.