WHO Consultation on the characterization of BCG vaccines

Overview

BCG vaccine is the only vaccine currently available for immunization against tuberculosis (TB) infections and has been used since the 1920s. During this time numerous sub-strains have evolved from the original strain and have been used for vaccine production. Not surprisingly, in view of the diversity of sub-strains, manufacturing processes, immunisation schedules and levels of exposure to environmental mycobacteria and virulent Mycobacterium tuberculosis infection, different levels of protective efficacy of BCG vaccines in adult populations have been reported. Nevertheless, as there is currently no alternative, BCG will remain in use in the foreseeable future and could continue to be used long term as a prime vaccine in a Prime-Boost immunization in conjunction with new TB vaccines. Because of this, the World Health Organisation (WHO) has recognized the need to improve both the characterization of this vaccine and the assays used for its quality control, taking into account recent advances in genetics and molecular biology.

An informal consultation on characterization of BCG vaccines was held on the 8 – 9 Dec 2004 at WHO Headquarters, Geneva, to review progress on the genetic characterization of BCG vaccines and to discuss the application of results to the improvement of quality control assays for BCG vaccines. The meeting was opened by Dr D. Wood, Coordinator, QSB, WHO. Dr M. Roumiantzeff was appointed Chairman, and both Drs M. Corbel and M. Ho were appointed Rapporteurs. The aims of this meeting were to:

• Discuss results of the multiplex PCR testing undertaken by NIBSC
• Review on-going research to identify any further work needed on the methodology for quality control of BCG vaccines, including molecular genetic characterisation.
• Review the current WHO requirements for production and control of BCG vaccines and consider changes required to reflect current state-of-the-art technology, in the light of recent developments. The Drafting Group would take the suggestions forward to produce a new draft set of recommendations which, after extensive consultation, would then be submitted to the Expert Committee on Biological Standardization (ECBS) as an update of the current document.
• Consider use of International Reference in the production and control of BCG vaccines and the need for such reference in research and development.