Severe complications of chickenpox in hospitalised children in the UK and Ireland

Aims: To estimate the annual incidence of hospitalisations due to severe complications of varicella, describe the complications and estimate annual mortality. Methods: Active surveillance throughout the UK and Ireland for 13 months by paediatricians notifying cases to the British Paediatric Surveillance Unit and completing a questionnaire. The case definition was any child aged <16 years hospitalised with complicated varicella, as defined by a list of conditions, or admitted to ICU/HDU with varicella. Results: 188 cases were notified for the surveillance period, of which 112 (0.82/100 000 children/year) met the case definition and were not duplicates. Confirmed cases had a median age of 3 years (range 0-14). The complications were: bacteraemia/septic shock (n=30), pneumonia (n=30), encephalitis (n=26), ataxia (n=25), toxic shock syndrome/toxin-mediated disease (n=14), necrotising fasciitis (n=7), purpura fulminans/disseminated coagulopathy (n=5), fulminant varicella (n=5) and neonatal varicella (n=3). 52 children (46%) had additional bacterial infections. Six deaths were due, or possibly due, to varicella, including one intrauterine death. Four of the other five children who died (ages 2-14 years) had a preexisting medical condition. Sequelae on discharge were reported for 41 cases (40%), most frequently ataxia or skin scarring. The median length of hospital stay was 7 days (range 1-68). Conclusions: This study provides a minimum estimate of severe complications and death resulting from varicella in children in the UK and Ireland. Most complications, excluding deaths, occur in otherwise healthy children and thus would be preventable only through a universal childhood immunisation programme.