This is a controlled cohort study to assess the effect of improved sanitation on oral rotavirus vaccine performance in low-income urban neighbourhoods of Maputo, Mozambique. The specific hypotheses are that: (1) access to improved sanitation is associated with increased oral rotavirus vaccine immunogenicity; (2) enteric infection concurrent to oral rotavirus vaccination is associated with reduced oral rotavirus vaccine immunogenicity; and (3) Environmental Enteric Dysfunction is associated with reduced oral rotavirus vaccine immunogenicity.