Attribution of reductions in malaria prevalence in Dar es Salaam, Tanzania – Authors' reply

We thank Mathieu Maheu-Giroux and Marcia Castro for their Correspondence about our Article.1 Regarding concerns about the stepped-wedge design of the larviciding scale-up in our study, we agree and also note that scale-up was not randomised, but rather introduced earliest to the best-prepared wards. However, such compromises are normal and healthy in pragmatic assessments of effectiveness under realistic programmatic conditions, rather than efficacy under artificially controlled experimental conditions. As acknowledged in the discussion and emphasised in the title, we also agree that evidence for window screening impact is purely observational, and that long-overdue, cluster-randomised, experimentally controlled analyses of well developed delivery practices for both these supplementary vector control measures are urgently needed.