Invasive Haemophilus influenzae type b disease in Sweden 1997–2003: Epidemiological trends and patterns in the post-vaccine era

Abstract

The introduction of vaccination against Haemophilus influenzae serotype b (Hib) in the Swedish childhood vaccination programme in 1992 resulted in a rapid 90% decline in meningitis cases. A recent rise in incidence in the UK underlines the need for continuing surveillance also in Sweden. Descriptive analysis of surveillance data for all invasive Hib infection cases notified in 1997–2003 was performed, with respect to age, gender, seasonality, geography and death; 185 cases (children 0–4 y: 37 cases) of invasive Hib disease were reported for an average incidence rate of 0.3 per 100,000 (children 0–4 y; 1.1). One fifth of the cases were children below 5 y of age, but two- thirds were over 30 y; median age was 49.5 y of age. 61% were female and 39% male (p = 0.0026). The sharp downward trend in incidence seen in the period 1993–1998 appears to have halted. During 2002 and 2003 there was a slight increase for children aged 0–4 y. There was also a highly significant female dominance, which has not been described before. Together with a shift in age distribution towards adults this points to women aged +30 y as a potential new risk group. This may reflect an increased risk owing to women being the primary carers of young children.