2-arm, double blind, placebo controlled, randomised trial, with 50 6-week-old infants per arm randomized to 98 days of daily iron (1.5mg/kg/day as ferrous sulphate) or placebo drops

Healthy infants will be randomised to receive daily supplementation from 6-20wks of either a) iron drops or b) placebo drops. Infants with significant illness or any clinical syndromes that would affect interpretation will be excluded. Low birthweight infants and infants born prematurely will not be excluded. Venous blood samples will be collected at enrollment (age 6 weeks) and after 14 weeks (98 days) of iron/placebo supplementation.

Participants will be visited daily in their villages by Fieldworkers (FW) to administer the iron/placebo dose and will interview mothers to complete a short health questionnaire. The iron will be dosed at 75% of WHO guideline dose (ie 1.5mg/kg/day). Weekly, a more detailed morbidity and breastfeeding questionnaires will be administered. Infants will be weighed and measured monthly, along with a faecal sample being taken.

During the daily visits, the FWs will record any adverse events (AEs) and ensure the safety of participants. If a child is found unwell or if the mother/guardian reports that the child is unwell, the study nurse will check on the child and decide on treatment/referral to the nearest health centre

Inclusion Criteria:

• Infants (male or female) from 6 weeks to 10 weeks of age.
• Breast fed infants (with plans to continue breastfeeding through 6 months of age).
• Parent/guardian with participant reside in study site area and are able and willing to adhere to all protocol visits and procedures (willingness to stay in the study area for the 14 weeks of supplementation).
• Healthy with no current illness and no chronic health problems.
• Signed or fingerprinted informed consent obtained from participants parent/guardian

Exclusion Criteria:

• Low birthweight babies (ie less than 2.5kg at birth) or babies born prematurely (ie less than 37 weeks) will NOT be excluded.
• Formula fed infants or those planning to terminate exclusive breast feeding before 6months of age.
• Acute illness (once acute illness is resolved, if appropriate, as per investigator assessment, participant may be re-revaluated for eligibility)
• Fever (for eligibility purpose defined as a body temperature greater than 37.5°C or mother report of fever) within 3 days prior to study initiation (once fever/acute illness is resolved, if appropriate, as per investigator assessment, participant may be re-revaluated for eligibility).
• Administration of any investigational drug within 30 days prior to study initiation or planned administration during the study period.
• Unwilling to avoid (their child to avoid) the ingestion of supplements or herbal/other traditional medications during the study period.
• Any history of or evidence for chronic clinically significant (as per investigator assessment) disorder or disease (including, but not limited to, immunodeficiency, autoimmunity, congenital abnormality, bleeding disorder, and pulmonary, cardiovascular, metabolic, neurologic, renal, or hepatic disease).
• Any history of human immunodeficiency virus, chronic hepatitis B or chronic hepatitis C infections.
• History of meningitis, seizures, Guillain-Barré syndrome, or other neurological disorders.
• Any condition that in the opinion of the investigator might compromise the safety or well- being of the participant or compromise adherence to protocol procedures

Data will be kept anonymous. There are currently no plans to share individual patient data beyond the investigator team. However, following all requisite approvals, an anonymized copy of the data can be made available for sharing. All key findings from this study will be submitted for publication in peer-reviewed journals.

This will be a two-arm, randomised, placebo-controlled double-blind study. Children will be randomised (1:1) to iron drops or placebo arm.