Farrington CP, Firth MJ, Moulton LH, Ravn H, Andersen PK, Evans S
Trop Med Int Health. 2009;14977-85
We review sources of bias which can affect non-randomized cohort studies of non-specific effects of vaccines on child mortality. Using examples from the literature on non-specific effects, we describe different sources of selection and information bias, and, where possible, outline analysis strategies to mitigate or eliminate such biases.
