The epidemiology of Haemophilus influenzae invasive disease in Scotland prior to immunisation.

Immunisation against Haemophilus influenzae b (Hib) was added to the UK childhood vaccination schedule on 1 October 1992. Based on reports of laboratory isolations from blood and/or CSF, the epidemiology of Haemophilus influenzae invasive disease in Scotland during the last full year before immunisation (1991) is reviewed. In children aged under five years the estimated incidence of infection (25.5 per 100,000) is higher than that previously reported from Scotland, but lower than estimates from Glasgow and other UK studies. However, the age-sex and seasonal distribution is consistent with previous surveys. As in England and Wales, there appears to be regional variation in incidence within Scotland, although this may simply reflect differences in the completeness of laboratory reporting. In addition to 113 laboratory reports of H. influenzae invasive infection, a retrospective search of hospital discharge data and death registrations identified a further 51 and two cases respectively, some of whom may be genuine. In spite of reservations about hospital discharge data, this raises the possibility that there may be an element of under-reporting by laboratories. With the advent of record linkage of hospital discharge data, it would be prudent to monitor the impact of the Hib vaccine programme using this data source in addition to laboratory reports and death registrations.