title: Varicella outbreak in the patients during group therapy: seroprevalence in a healthcare system during breakthrough varicella occurrence.
abstract: OBJECTIVE
  There are different principles regarding varicella vaccination depending on social requirements. This study was performed to report a case of breakthrough chickenpox outbreak among a group of people in the healthcare center and also evaluate the seroprevalence of patients who have been managed with chronic neurological diseases in this center.
  
  
  METHODS
  We included patients diagnosed with varicella in April 2009 as an index cases and investigated the past history for chickenpox and the varicella-specific IgG. Sixty-two patients (children) and 156 healthcare workers who may have had possible contact with the index cases were also investigated for.
  
  
  RESULTS
  We investigated the seroprevalence of 62 patients not affected by the outbreak. The varicella vaccination rate in children was 90.3%. Sixty-one point three percent of all patients were seropositive and 63.6% of these patients were aged between 12 and 23 months and 87.5% were aged between 24 and 35 months. Seropositive rate was decreased for patients aged between 36 and 59 months while the seropositive prevalence has increased for patients over 5 years old. Over 90% of the adults investigated were seropositive. IgG seronegative despite vaccination was 32.1% (18 persons).
  
  
  CONCLUSIONS
  Breakthrough varicella outbreak can have huge impact in healthcare centers with affiliated group housing. We need to investigate vaccination status and immunogenicity according to ages and reflect appropriately on vaccination policy taking into consideration of social and medical requirements in the local area.
authors.affiliation: Department of Pediatrics, Severance Children's Hospital,Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Cheong Soo
authors.initials: CS
authors.lastname: Park
authors.forename: Dong Soo
authors.initials: DS
authors.lastname: Kim
authors.forename: Ki Hwan
authors.initials: KH
authors.lastname: Kim
keywords: Breakthrough; Chickenpox; Immunization; Seroprevalence; Varicella