Bacterial infections among young infants, including sepsis, meningitis, and pneumonia, continue to cause a substantial number of deaths globally. Zinc supplementation in combination with standard antibiotic therapy may represent a new intervention to reduce mortality and improve treatment outcomes for young infants with clinical severe infection. The Investigators will conduct a randomized, double-blind, placebo-controlled trial of zinc supplementation among young infants 0-59 days with severe clinical infection. The trial will enroll 3,250 Tanzanian infants hospitalized with clinical severe infection as defined by WHO Integrated Management of Childhood Illness (IMCI) guidelines. Enrolled infants will receive standard clinical management including antibiotics and will be randomized to receive either a 14-day course of twice-daily 5 mg elemental zinc (10 mg per day) or a matching placebo regimen.