Abstract
AIMS: To document the immunogenicity and persistence of antibody to polyribosyl-ribitol phosphate (PRP) as well as the clinical protection against invasive Haemophilus influenzae type b (Hib) disease in premature infants immunised at the routine schedule. METHODS: Blood was obtained at 2, 5, 12, and 64 months of age from a cohort of prematurely born infants (