Haemophilus influenzae serotype B (Hib) seroprevalence in England and Wales in 2009

A national seroprevalence study was performed to determine the prevalence of Haemophilus influenzae type b (Hib) antibodies in England and Wales in 2009, when Hib disease incidence was the lowest ever recorded. A total of 2,693 anonymised residual sera from routine diagnostic testing submitted by participating National Health Service hospital laboratories were tested for Hib anti-polyribosyl-ribitol phosphate (PRP) IgG antibodies using a fluorescent bead assay. Median anti-PRP IgG concentrations were highest in toddlers aged 1-4 years (2.65 µg/ml), followed by children aged 5-9 years (1.95 µg/ml). Antibody concentrations were significantly lower after this age, but were still significantly higher among 10-19 year-olds (0.54 µg/ml) compared with adults aged >20 years (0.16 µg/ml; p