Data and sample collection
Use of non-study antibiotics by study children, defined as any antibiotic that was not part of the study intervention, was identified using a standardized questionnaire at monthly visits. Child lengths using measuring boards and weights using digital scales were measured every three months. Stool samples were collected at 6, 6.5, 12, 12.5, and 18 months of age, and 1,141 children contributed at least 1 sample. The 6 and 12 month samples were required to be collected prior to administration of study antimicrobials. The study protocol was approved by the National Institute for Medical Research (NIMR) of Tanzania and the Tanzanian Food and Drug Administration (TFDA) and the Institutional Review Board at the University of Virginia. Mothers gave written informed consent to participate either during pregnancy or at the time of enrollment. The study was registered at ClinicalTrials.gov: NCT03268902.