Infection: A Case-Control Study in

Invasive Haemophilus influenzae (HI) infection is still an important cause of worldwide morbidity and mortal-ity in childhood. Since the introduction of general vac-cination against Haemophilus influenzae type b (Hib) in some areas, a decrease of HI incidence has been documented.1,2 Most of the invasive HI infections are due to type b (Hib) which may cause secondary cases in day-care centres and households.3–5 In populations such as eskimos and navajo indians with a very high incidence of invasive HI infection, meningitis is the most common form with a peak incidence below the age of one year6,7 while epiglottitis is seen in populations with a low incidence and with a peak around the age of 3 years.8,9 One of the most important risk factors for disease is subsequently young age. Other risk factors have been mentioned such as day-care attendance,10–13 passive smoking,13,14 household crowding,10–12 presence of siblings younger than 7 years of age, history of pre-vious hospitalization or otitis media and breastfeeding for less than 6 months.15 In Sweden, Salwén et al. reported a 2.5 fold increase in incidence of HI menigitis between 1970 and 19801