Estimates of influenza vaccine effectiveness in primary care in Scotland vary with clinical or laboratory endpoint and method-Experience across the 2010/11 season

Our approach illustrated the ability to achieve relatively consistent estimates of seasonal influenza VE using both specific and less specific outcomes. Construction of a propensity score and use for bias adjustment increased the estimate of ILI VE estimated from the Cox model and made estimates more similar to the Poisson approach, which models differences in consultation behaviour of vaccinated individuals more inherently in its structure. VE estimation for the same data was found to vary by methodology which should be noted when comparing results from different studies and countries.