Retest programmes that involve animal testing should be designed to minimise the use and the suffering of the tested animals as much as possible, in line with Directive 2010/63/EU on the protection of animals used for scientific purposes. This Annex focuses on reduction of animal use through the retest strategy. Other 3R approaches should be considered (e.g. testing the bulk instead of several final filling batches, or application of the humane endpoint for symptomatic animals), but are not described in this document.