Enhancing the reproducibility of serological methods used to evaluate immunogenicity of pandemic H1N1 influenza vaccines-An effective EU regulatory approach

► Lab-to-Lab reproducibility of haemagglutination inhibition and neutralisation assay. ► Assays for evaluation of influenza vaccine immunogenicity for regulatory approval. ► EMA central retesting: control authorities retest sera from pandemic vaccine trials. ► Almost 2000 sera from all EU manufacturers retested: high variability of results. ► Reproducibility markedly improved by inclusion of calibrated antiserum standard.