This report presents the recommendations of a WHO Expert Committee commissioned to coordinate activities leading to the adoption of international recommendations to assure the quality, safety and efficacy of vaccines, blood products and other biological medicines, and the establishment of international biological reference standards.<br><br>The report starts with a discussion of general issues brought to the Committee's attention and provides information on the status and development of reference materials for various antibodies, antigens, blood products and related substances, cytokines, growth factors, and endocrinological substances. The second part of the report, of particular relevance to manufacturers and national regulatory authorities, contains WHO recommendations and guidelines on human papillomavirus vaccines; meningococcal A conjugate vaccines; and stability evaluation of vaccines.<br><br>Also included are a list of recommendations, guidelines and other documents for biological substances used in medicines, and of international standards and reference reagent for biological substances.