Invasive haemophilus influenzae infection following HIB Immunisation
In September 1992, the BPSU included invasive H influenzae infection occurring after Hib immunisation in its reporting scheme. In 1995, surveillance also included cases occurring in unvaccinated children. The data collected allowed the estimation of vaccine effectiveness, in relation to both the pre-vaccine era and incidence of cases in the unvaccinated population. In the later years of the study, there was confidence that estimates of efficacy truly represented the effect of the primary infant series.
Lead investigator
P T Heath
About the study
The introduction of Haemophilus influenzae type b conjugate vaccines into the national immunisation schedules of the United Kingdom (UK) and the Republic of Ireland (ROI) happened in October 1992. Infants had a three-dose primary course without boosting, in line with the routine accelerated schedule for other infant immunisations at 2, 3 and 4 months of age. The first year of the programme also included a catch-up campaign, giving a single dose of conjugate vaccine to children aged 1 to 4 years.
In September 1992, the BPSU included invasive H influenzae infection occurring after Hib immunisation in its reporting scheme. In 1995, surveillance also included cases occurring in unvaccinated children.
The data collected allowed the estimation of vaccine effectiveness, in relation to both the pre-vaccine era and incidence of cases in the unvaccinated population. In the later years of the study, there was confidence that estimates of efficacy truly represented the effect of the primary infant series. This was because the children who participated in the initial catch-up campaign had grown older. This information also allowed the research team to make some assessment of the duration of protection offered by a primary conjugate vaccination series without a booster.
At the time, ongoing post-licensure surveillance played an important further role in monitoring the longer-term effects of an immunisation programme on the population, in particular, ensuring that no new populations of ‘susceptibles’ were generated.
The study aimed to identify cases of invasive H influenzae disease occurring in children regardless of their vaccination status, enabling:
- Estimation of the effectiveness of Hib conjugate vaccines in British and Irish children.
- Determination of the importance of disease due to non-type B H influenzae.
- Documentation of host factors and the clinical presentation of the disease. In cases of vaccine failure, the collection of acute and convalescent concentrations of Hib antibody.
Duration
October 1992 – October 2000
Published papers