Varicella in pediatric oncology patients in the post-vaccine era-Analysis of routine hospital data from Bavaria (Germany), 2005-2011.

Varicella in oncology patients can result in serious complications. We analyzed trends in hospitalization rates and characteristics of pediatric oncology and non-oncology patients hospitalized with varicella during the first 7 years after introduction of routine varicella vaccination. Our data included children <17 years of age with an International Classification of Diseases and Related Health Problems, 10th Revision (ICD-10) main or secondary discharge diagnosis of varicella identified by annual database queries in 22-29 pediatric hospitals in Bavaria (Germany) in 2005-2011. Of a total of 1,245 varicella-associated hospitalizations, 42 children (median age 4 years, interquartile range 3-5) had an underlying malignancy (67% with acute lymphoblastic leukemia). Overall, additional diagnoses potentially associated with varicella were reported less often in oncology than in non-oncology varicella patients (62% vs. 77%, p = 0.041), suggesting earlier hospitalization of high-risk patients. Acute hematological diagnoses (29% vs. 3%, p < 0.001) and coinfections (invasive 12% vs. 2%, p = 0.001; noninvasive 19% vs. 8%, p = 0.019) were more frequent, whereas neurological (5% vs. 19%, p = 0.023) and upper respiratory tract diagnoses (2% vs. 16%, p = 0.014) were less frequent in oncology compared to non-oncology varicella patients. Oncology varicella patients showed a longer hospital stay (median 5 vs. 3 days, p < 0.001). Hospitalization rates in non-oncology varicella patients declined constantly since 2006, from 114.8 (2006) to 30.5 (2011) per 1,000 pediatric beds. The rates of varicella-associated hospitalizations in oncology patients indicated an overall decreasing trend (3.8, 1.9, 4.6, 3.5, 0.4, 2.1 and 0.6 cases per 1,000 pediatric beds in 2005-2011). Thus, pediatric oncology patients potentially profit from herd protection effects, resulting from increasing vaccine coverage in the general population.