WHO/KFDA workshop on stability evaluation of vaccines, Seoul, Korea, 23-25 April 2008

In April 2008, the World Health Organization and the Korea Food & Drug Administration jointly organized a workshop on evaluating vaccine stability. The main objective of the workshop was to facilitate implementing newly established WHO guidelines. The value of stability studies in understanding vaccine characteristics, establishing shelf-life and release specifications, and monitoring the stability post-market was well explained. Optimal designs for goal-based stability studies were proposed and appropriate statistical analyses presented. A statistical model (the term "estimation model" was adopted) based on regression analysis of potency loss over storage time elapsed, was elaborated for describing the stability profile of vaccines. This model was believed to provide a more precise description of the stability characteristics of a vaccine than the current "compliance model". The use of both models was discussed in relation to specific examples and case studies. A document format for assisting standardized stability report was discussed as a possible annex to the WHO stability guidelines adopted in 2006. The participants agreed that a future revision of vaccine stability guidance should highlight the estimation model and that WHO should provide additional training to support national regulatory authorities with statistical design and analysis, and to assist their transition from the compliance model towards wider use of the estimation model.