Low birth weight (less than 2500 g) or sick newborn infants should be given BCG and polio vaccine when they are well enough to be discharged home from hospital. By this time some preterm infants may already be a few months old. After discharge they can follow the routine immunisation schedule. If a preterm infant is older than 6 weeks when it is discharged home, the routine 6 week immunisations can be given at discharge and then repeated at 4 week intervals. It is rare that preterm infants need immunisation before they are ready for discharge.