Storage of stool samples for evaluation of helminth status following completion of the study is also not feasible for several reasons. Most importantly, there are ethical issues related to the collection of samples (and therefore the potential knowledge of infection status) without providing directed therapy. If helminth status is known (or potentially known), the standard of care in Kenya would change from symptomatic screening and treatment to definitive pathogen directed therapy. This would alter the intervention arms in the current study. In addition, the most common helminth at all of the sites sampled in our previous study was hookworm. Hookworm eggs are fragile and rapidly degrade. None of the currently available techniques will preserve hookworm eggs reliably and so any delayed evaluation of helminth infection status is likely to miss many infections and therefore not provide any additional useful information.