Potency estimation of vaccine batches remains unaffected by anesthesia for intracerebral injection

Potency testing of rabies and whole-cell pertussis vaccine batches is still performed by an intracerebral (i.c.) challenge test, in conformity with international regulatory requirements. For the i.c. injection, the use of anesthesia is strongly recommended to alleviate the severe pain induced by the procedure. Today, anesthesia is not consistently mentioned in regulatory requirements, in contrast to the times when the potency tests were developed. The introduction of anesthesia is hampered, due to the lack of data on a hypothetical impact of anesthesia on potency estimation. Here, we show the comparative analysis of the extensive batch release data set of a rabies vaccine for human use that was tested in two laboratories of which only one applied anesthesia. In essence, we find that the mean batch test results were similar to each other, demonstrating that anesthesia for i.c. injection does not interfere with potency estimation. Consequently, we recommend the update of regulatory requirements and protocols and support the implementation of anesthesia for i.c. injection.