Epidemiological studies of the non-specific effects of vaccines: II--methodological issues in the design and analysis of cohort studies.

摘要

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.