Expert consultants under the direction of WHO have recommended evaluating oral-only antibiotic regimes as alternatives to injectable antibiotics for infants with suspected serious bacterial infection. Thus, there is an urgent need to evaluate the effectiveness of early identification and innovative but simple antibiotic regimens to treat young infants with suspected serious bacterial infection in low and middle income countries. The proposed team of investigators will work with the NICHD and other sites of the Global Network for Women's and Children's Health Research to design, prioritize, plan, implement, analyze, interpret, and report innovative randomized trials and observational studies that are likely to improve maternal and childhood survival and reduce important morbidities.