RT Journal Article SR Electronic(1) A1 De Serres, G A1 Skowronski, D M A1 Wu, X W A1 Ambrose, C S YR 2013 T1 The test-negative design: validity, accuracy and precision of vaccine efficacy estimates compared to the gold standard of randomised placebo-controlled clinical trials JF Eurosurveillance VO 18 IS 37 SP 20585 OP DO https://doi.org/10.2807/1560-7917.ES2013.18.37.20585 UL https://www.eurosurveillance.org/content/10.2807/1560-7917.ES2013.18.37.20585