Specific Varicella-Related Complications and Their Decrease in Hospitalized Children after the Introduction of General Varicella Vaccination: Results from a Multicenter Pediatric Hospital Surveillance Study in Bavaria (Germany)

Abstract

Universal varicella vaccination (UVV) for children introduced in Germany in 2004 resulted in a significant overall decline of varicella-related hospitalizations (VRHs). We investigated the incidence of specific types of varicella-related complications (VRCs) in hospitalized children and the impact of UVV on VRCs during the first 7 years of UVV. Children\u2009<\u200917 years of age hospitalized with an ICD-10-based (International Classification of Diseases, 10th Revision) discharge diagnosis of varicella were identified as VRH in pediatric hospitals in Bavaria by annual standardized data queries of the hospital databases (2005–2011). For each VRH, the hospitals reported basic demographic data, duration of hospital stay, all diagnostic and procedural codes, and outcome. VRCs were reported overall, per year, and by immune status. Complication rates were calculated as mean number per complication category per hospital and per year; VRC trends over time were assessed by linear regression. Between 78% (2005) and 61% (2011) of Bavarian hospitals participated and reported a total of 1263 VRHs. Specific VRCs were reported in 954 (76%) children. Complication rates per hospital and year decreased from 6.7 [95% confidence interval (CI): 5.1–8.3] in 2005 to 1.5 (95% CI: 0.8–2.3) in 2011, with the strongest reduction of 90% in children\u2009<\u20095 years of age from 5.3 (95% CI: 4.0–6.6) in 2005 to 0.5 (95% CI: 0.1–0.9) in 2011. Significant decreases were observed for children with upper respiratory tract (URT, by 97%), lower respiratory tract (LRT, by 90%), skin (by 81%), gastrointestinal (by 78%), and neurologic (by 65%) VRCs. Forty-eight children with VRCs were immunocompromised; their annual rate decreased by 87%. Corresponding to increasing varicella vaccination coverage in the population, the incidence of VRC decreased by 77% from 2005 to 2011, with the most substantial decrease in the target group for UVV. Within 7 years, UVV in Germany led to a decrease of about 77% of all types of VRCs, with the highest reductions observed for VRCs of the respiratory tract.