The Burden of Varicella Complications Before the Introduction of Routine Varicella Vaccination in Germany

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Abstract
Background: The true burden of varicella complications in Germany is not known. We investigated the incidence and pattern of varicella complications in children and adolescents using 3 independent surveillance sources. Methods: Prospective nationwide surveillance in all pediatric hospitals through the German Pediatric Surveillance Unit [Erhebungseinheit für Seltene Pädiatrische Erkrankungen in Deutschland (ESPED)] was used to ascertain hospitalized varicella cases in children ≤16 years of age between January 2003 and December 2004. In the federal state, North-Rhine Westphalia (NRW), a practice sentinel network [European Diabetes Study Group (EURODIAB)] and pediatric hospital based International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10) surveillance were additionally used to refine incidence estimates via capture-recapture methodology. Results: A total of 918 hospitalized varicella patients (male-to-female: 55%/45%) with a median age of 3.3 years (interquartile range, 1.4–5.2) and a median hospital stay of 5 days (interquartile range, 3–8) were reported. Varicella associated complications occurred in 80% of the hospitalizations, most frequently being neurologic (25.4%), skin infectious (23.2%), and gastrointestinal tract complications (15.0%). Most hospitalizations (77%) occurred in previously healthy children. A predisposing condition existed in 207 children (23%): immunosuppression 7%, atopic dermatitis 7%, and other underlying chronic conditions 9%. Severity of varicella complications was related to increasing age and immunosuppression. Permanent or possible sequelae were reported in 15 (1.7%) and 78 (8.7%) of all children, respectively; 10 children died. Capture-recapture analyses yielded an incidence of 14.1 (95% confidence interval, 9.7–18.6) varicella hospitalizations/100,000 children, corresponding to 1996 (95% confidence interval, 1363–2629) varicella-related hospitalizations per year in Germany. Conclusions: These data show that the severity of varicella complications in healthy children has been previously underestimated.