Two decades of experience with the Haemophilus influenzae serotype b conjugate vaccine in the United Kingdom

Abstract

Background: The Haemophilus influenzae serotype b (Hib) conjugate vaccine was introduced into the UK national childhood immunization program in 1992 after clinical trials reported the vaccine to be highly immunogenic in infants as young as two months of age.

Objective: The goal of this study was to describe and comment on the impact of routine Hib immunization on the epidemiology of invasive Hib disease in the United Kingdom. In addition, the development of Hib polysaccharide and conjugate vaccines was reviewed.

Methods: A literature search was conducted of PubMed for invasive Hib disease epidemiology in the United Kingdom. The UK Health Protection Agency Web site was also searched for relevant publications.

Results: The incidence of invasive Hib incidence in children aged <5 years fell from 21/100,000 to 44/100,000 in the prevaccine era to 0.63/100,000 in 1998, with an estimated vaccine failure rate of 2.2/100,000 vaccinees. After 1999, however, invasive Hib disease increased, particularly in toddlers, and peaked in 2003. Potential reasons for the resurgence included a greater-than-expected decline in Hib antibodies after primary immunization, waning of herd immunity offered by the initial catch-up campaign, and use of a less immunogenic Hib combination vaccine containing acellular pertussis in 2000-2001. In response to the resurgence, a Hib combination vaccine containing whole-cell pertussis was reintroduced in 2002, followed by a childhood Hib booster campaign in 2003. In 2004, the recommended infant vaccine was changed to a different Hib/acellular pertussis combination vaccine containing inactivated polio, which had a satisfactory Hib response, was less reactogenic, and eliminated the risk of vaccine-associated paralytic poliomyelitis. This action was followed by introduction of a routine 12-month Hib booster in 2006. Together, these measures led to a decline in invasive Hib disease across all age groups. In 2010, there were only 30 invasive Hib cases, with 6 reported in children aged <5 years and no deaths in this age group since 2007.

Conclusions: Control of Hib disease is currently the best that has been achieved since the introduction of the routine Hib vaccination almost 20 years ago.