Severe chickenpox disease and seroprevalence in Sweden - implications for general vaccination

Objectives: To describe the current panorama of severe chickenpox disease and seroprevalence in Sweden, as a basis for the approaching decision on universal vaccination.

Methods: Patients discharged with an International Classification of Diseases 10th revision-code for chickenpox (B01-B01.9) in eight pediatric and infectious diseases departments in Stockholm and Gothenburg in 2012-2014 were included in the study and their medical charts were reviewed. Further, residual serum samples collected from 11 laboratories across Sweden were analyzed for varicella zoster IgG-antibodies to investigate age-specific seroprevalence.

Results: A total of 218 children and 46 adults were included in this hospital-based study; 87.2% of children and 63.0% of adults had complications. An underlying condition was not associated with an increased risk of complication. Dehydration (31.7%), bacterial skin infections (29.8%) and neurological involvement (20.6%) were the most frequent complications in children. Among adult cases, 63% were born abroad. The seroepidemiological analysis included 957 patient samples. Seroprevalence was 66.7% at 5 years and 91.5% at 12 years. Infants and adolescents/adults were overrepresented among admitted patients compared to seroprevalence data.

Conclusions: Half of all complications in hospitalized chickenpox cases were seen in previously healthy children, which supports universal childhood vaccination. Adult migrants was a risk group for chickenpox hospitalization. Age-specific seroprevalence was similar to neighboring countries.