Informed consent and cluster-randomized trials.

We argue that cluster-randomized trials are an important methodology, essential to the evaluation of many public health interventions. However, in the case of at least some cluster-randomized trials, it is not possible, or is incompatible with the aims of the study, to obtain individual informed consent. This should not necessarily be seen as an impediment to ethical approval, providing that sufficient justification is given for this omission. We further argue that it should be the institutional review board's task to evaluate whether the protocol is sufficiently justified to proceed without consent and that this is preferable to any reliance on community consent or other means of proxy consent.