RISK-FACTORS FOR INVASIVE HAEMOPHILUS-INFLUENZAE DISEASE AMONG CHILDREN 2-16 YEARS OF AGE IN THE VACCINE ERA, SWITZERLAND 1991-1993

Background. Continued surveillance, and detailed investigation of dire ct and indirect effects of conjugated vaccines and risk factors for in vasive H.influenzae serotype b (Hib) disease in the vaccine era are im portant. Methods. 143 cases with invasive disease between 1991 and 199 3 aged 2-16 years were selected retrospectively from a large incidence trend study, Controls (n = 336) were recruited from local vital regis tries and matched to cases for age, gender, and residence. Hib vaccina tion histories among study subjects and their siblings and other socio demographic variables were obtained by questionnaires completed by the parents of these children. Adjusted odds ratio (OR) estimates were ca lculated by conditional logistic regression analysis. Results. Most va ccinated subjects had received the Polysaccharide-Diphtheria Toroid va ccine and estimated vaccine efficacy was high (95%; 95% confidence int erval [CI] 60-99%). Also, the results suggested that protection afford ed by vaccination against Hib extended to the family members of vaccin ated children, School attendance was found to be protective against in vasive Hib disease (OR : 0.33; CI : 0.14-0.75). Cases more often than controls reported sufferring from asthma and allergies (OR : 4.8; CI : 1.2-19.4). Conclusions. Post-licensure vaccine efficacy is high among children greater than or equal to 2 years of age, The observed associ ation between asthma and epiglottitis is novel and deserves further in vestigation.