Complications of varicella in a defined central European population.

AIMS To describe complications of varicella requiring hospitalisation in a defined population (canton of Bern) and to compare the hospitalisation rates for varicella with published data. METHODS Retrospective analysis of hospital records of patients less than 16 years of age admitted with complications of varicella to the hospitals serving this population (University Children's Hospital of Bern and the Wildermeth Children's Hospital of Biel, Switzerland), and calculation of hospitalisation rates for varicella and its complications based on birth rates and varicella antibody prevalence rates. RESULTS From 1986 to 1996, 113 cases (median age, 5.6 years) were identified. Younger siblings were overrepresented (odds ratio (OR), 1.42; 95% confidence interval (CI), 1.09 to 1.84). Central nervous system (CNS) complications (26 patients; 23%) were found predominantly in previously healthy children (relative risk, 7.1; 95% CI, 1.01 to 49.86). Group A beta haemolytic streptococci were recovered from only one of 35 patients with bacterial complications. The hospitalisation rates for primary varicella (9.2/10(4) cases; 95% CI, 7.4 to 11/10(4), skin infections (2.0/10(4) cases; 95% CI, 1.2 to 2.9/10(4), and pneumonia (0.8/10(4) cases; 95% CI, 0.3 to 1.3/10(4)) were significantly lower than reported previously. The CNS complication rate (2.2/10(4) cases; 95% CI, 1.3 to 3.1/10(4) was among the highest rates reported. CONCLUSIONS The low hospitalisation rate in comparison with studies from elsewhere indicates that there is a large regional variability in complications associated with varicella. Such data should be taken into consideration when local varicella immunisation strategies are developed.