Amendment to Annex 5 - Recommendations to assure the quality, safety and efficacy of live attenuated yellow fever vaccines,  TRS No 978

Overview

The WHO Recommendations to assure the quality, safety and efficacy of live attenuated yellow fever vaccines were adopted in 2010. Appendix 2 of these Recommendations addresses the testing of new virus master and working seed lots in non-human primates. Specifically, the appendix sets out the ways in which such lots should be tested for viscerotropism, immunogenicity and neurotropism, both in terms of clinical evidence and histological lesions, based on comparison against a reference virus approved by the NRA. Following reported discrepancies in the clinical scoring of monkeys during the assessment of working seed lots, WHO received a request from one yellow fever vaccine manufacturer to align the neurotropism assessment outlined in the 2010 Recommendations with that used for the neurovirulence testing of oral poliomyelitis vaccine seed lots in which clinical signs are recorded but do not form part of the assessment or pass/fail criteria.