Prospective surveillance of hospitalisations associated with varicella-zoster virus infections in children and adolescents

Our goal was to determine the epidemiology of severe varicella-zoster virus (VZV) infections in hospitalised paediatric patients. Admissions associated with VZV infection of patients aged 0-16 years were reported by all 38 paediatric units in Switzerland to the Swiss Paediatric Surveillance Unit (SPSU) during 3 consecutive years (4/2000-3/2003). We verified completeness of reporting by capture-recapture analysis with patient records identified by ICD-10 codes. Outcome of illness was assessed 6 months after hospitalisation. A total of 335 cases (235 identified by SPSU reports, 100 by ICD-10 code) were included in this study. Mean age of patients was 4.1 years (median 3.5 years, range 0-16 years); 54% were male. Some 293 (87%) patients presented with chickenpox, 42 (13%) with herpes zoster and 291 (87%) patients were not immunocompromised. A total of 319 complications occurred in 237 (71%) patients: secondary bacterial infections (n = 109); central nervous system involvement (n = 76); VZV pneumonitis (n = 7); others (n = 127). Eleven (3 %) patients required intensive care and three died. On follow-up, 303 (96%) of 315 patients had completely recovered; sequelae were present in 12 (4%) patients. The calculated hospitalisation rate was 13 per 104 cases. Conclusion: This study describes a sizeable hospitalisation and complication rate of varicella-zoster virus infections and provides a solid basis for future immunisation recommendations in Switzerland.