- Dose Group 4 (Cohort 1), only: Infant is breastfeeding at time of enrollment or mother has indicated an intention to initiate breastfeeding. Note: if a child is breastfed prior to known maternal diagnosis (in the case of a woman diagnosed in the intrapartum period), the child is still eligible as long as breastfeeding is stopped by the time the child is enrolled and there is no plan to resume breast milk feeding.