Vaccine testing without animal experiments?

Vaccines must provide effective protection against disease without any harmful side effects. Antigen purity is a crucial factor which until now has had to be tested on animals. However, recent scientific developments allow the use of alternatives to animal experiments in many cases, e.g. poultry vaccine purity testing. The in vitro Polymerase Chain Reaction method (PCR) is one advance which could reduce the number of animal experiments.