The burden of chickenpox disease in Sweden

BACKGROUND Chickenpox vaccine is not included in the routine childhood vaccination programme in Sweden. The aim of this study was to estimate the baseline of national chickenpox disease burden, as comprehensive studies, required for an assessment regarding vaccine introduction, are lacking. METHODS We used available health care registers and databases; the death register, hospitalisations register, communicable disease notifications database, Stockholm County registers on consultations in specialist and primary care, temporary parental benefit to care for a sick child, and searches on the health care system's website. From each data source, records regarding chickenpox were identified and extracted, either using relevant diagnosis codes (ICD-10) or key words. A descriptive analysis with regards to number of cases and incidence, severity, and seasonality, was carried out covering the time period 2007 to 2013. RESULTS There were on average 333 patients hospitalised annually due to chickenpox, yielding a hospitalisation rate of 3.56/100,000 person-years. We found a slight male predominance in hospitalised cases. The highest hospitalisation rate was seen in 1 year-olds, whereas the peak in primary care consultations was in 2 year-olds. Nearly a quarter of children had parents who reported absence from work to care for them when sick with chickenpox. The average yearly death rate from chickenpox was 0.034/100,000 person-years. The duration of hospital stay increased with age. The seasonality in number of searches on the health care website corresponded well with hospitalisations and primary care consultations with peaks in spring. CONCLUSIONS This study shows chickenpox death and hospitalisation rates in range with other European countries without routine vaccination. Swedish children fall ill with chickenpox at a very young age. The study provides essential input for future discussions on the introduction of routine chickenpox vaccination in Sweden.