•Relevance: We now better understan

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Relevance: We now better understand the limitations of laboratory animal models to measure vaccine characteristics relevant for predicting their safety and efficacy in humans and target animals (in the case of veterinary vaccines). In fact, several of the models in use have never been properly validated as regards their predictive value for clinical efficacy [8].
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Ethics and costs: The use of laboratory animals poses ethical concerns, is expensive, time consuming and requires skilled staff and sophisticated experimental facilities.
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Reference preparation: Some of the currently used animal models that include the use of an international reference preparation do not meet the fundamental criteria defined by Jerne and Maaløe [9]for bioassays that test and reference vaccine should behave as unknown dilutions of each other.
It is believed that the extension of the consistency approach to conventional products will (a) introduce a more stringent system to manage the quality of the vaccine lots produced and (b) lead ultimately to a substantial reduction in animal usage. This approach aims to identify the critical indicators of a safe and effective product and to monitor these indicators during production, thus reducing the need for extensive final lot testing, often associated with the use of animals. Consistency builds on elements of information obtained during product development (including clinical testing) and routine production using suitable analytical tools and the continuous evaluation of data generated over time (trend analysis).