ID/IDA affects many young children in Africa. Vaccines provide tremendous benefits in LMIC; however, they currently fail to reach their full potential. We need to better understand the causes of vaccine failure, in order to develop new strategies to improve vaccine immunogenicity.

This study will contribute to children's health by: (1) providing updated guidelines to better define the prevalence of ID/IDA in early infancy, and its safe and effective control using iron; and (2) providing a new approach to improve response to pediatric vaccines in LMIC, by ensuring adequate iron status at time of vaccination.

Two major pediatric public health goals in LMIC are increasing immunization effectiveness and reducing ID/IDA in children. ID/IDA affects many young children in Africa. Current guidelines do not recommend routine testing of hemoglobin in early infancy, as it is generally believed that most infants are born with adequate iron stores to last 6 months. However, many African infants are born with low iron stores and ID/IDA may develop earlier than generally appreciated, within 2-3 months after birth. Vaccines provide tremendous benefits in LMIC; however, they currently fail to reach their full potential. We need to better understand the causes of vaccine failure, in order to develop new strategies to improve vaccine immunogenicity. Despite lower efficacy in LMIC, these vaccines provide a major benefit because the disease burden is so high; however, if approaches can be found to improve immunogenicity, these vaccines would be even more powerful.

For this study, 6 weeks old infants will be randomly assigned to two study groups. Group 1 will receive iron at time of pediatric vaccinations from age 6-24 weeks. Group 2 will receive no iron at time of pediatric vaccinations. All infants will receive a multivitamin syrup from age 6-24 weeks. All infants remaining ID/IDA at age 24 weeks will receive iron. Infants will be followed-up until age 52 weeks.

Inclusion Criteria:

• Mother at least ≥15 years of age.
• 6 weeks (+/- 3 days) of age
• Iron deficient (erythrocyte zinc protoporphyrin (ZnPP) >61 μmol/mol heme)
• With or without anemia, but not severely anemic (Hb >70 g/L)
• No malaria
• No medical condition that precludes study involvement
• Mother HIV negative
• Vaginal delivery
• No iron supplementation prior to study enrolment
• Not wasted (length for height z score of ≥-2)
• Not underweight (weight for age z score ≥-2)
• From the hospital record, term or late preterm delivery (≥34 weeks)
• Full-time breastfed at least until the screening
• No vaccines beyond the birth dose of OPV and BCG prior to enrolment