T helper cells and efficacy of Haemophilus influenzae type b conjugate vaccination

Abstract

A small number of fully vaccinated children in the UK have experienced invasive Haemophilus influenzae type b (Hib) infection. A rise in disease in recent years has been associated with lower vaccine-induced antibody levels over the first 5 years of life, forcing greater dependence on immunological memory for protection. This has necessitated the introduction of a catch-up campaign, designed to boost immunity in children aged 6 months to 4 years of age. We suggest that the conjugate vaccine's inability to induce pathogen specific helper T cells, combined with a loss of natural boosting due to reduced circulation of Hib, may have contributed to the rising incidence of invasive disease 10 year..