REVIEW The UK Hib vaccine experience

Haemophilus influenzae type b (Hib) is an important pathogen in children <5 years of age. The Hib conjugate vaccines were the first polysaccharide– protein conjugate vaccines to be used in routine childhood schedules. Their introduction in the UK in 1992 has resulted in the near elimination of Hib disease. The UK Hib vaccine programme has a number of unique features including an accelerated schedule, absence of a booster dose, and the inclusion of a catch up component at the beginning of the programme. Collaboration between UK paediatricians, microbiologists, and public health physicians has allowed active national surveillance of Haemophilus influenzae disease and enabled important conclusions to be drawn. These include high vaccine effectiveness, the presence of herd immunity, and the frequency of risk factors in cases of vaccine failure and in cases of invasive disease due to non-b H influenzae. Parallel studies have shown the immunogenicity, induction of immunological memory, and persistence of immunity following vaccination at the UK schedule, as well as measuring the impact of vaccination on pharyngeal Hib carriage. Cases continue to occur and complacency is ill advised, particularly as other vaccines and combinations are introduced. Surveillance of H influenzae disease in the UK remains important. Doctors training in paediatrics in the UK inthe year 2002 are unlikely to see a case ofepiglottitis. Nor are they likely to see cases of meningitis, cellulitis, osteomyelitis, or septic arthritis caused by the bacterium Haemophilus influenzae type b (Hib). Yet prior to 1992 Hib was the most common cause of meningitis in child-hood, almost the exclusive cause of epiglottitis, and a common cause of cellulitis and bone and joint infections. The introduction of Hib conjugate vaccines in the UK has almost eliminated this pathogen. What lessons has the UK Hib vaccine experience taught us and what issues remain