title: Varicella serology among school age children with a negative or uncertain history of chickenpox.
abstract: BACKGROUND
  Clinicians who offer varicella vaccination to school age children face the dilemma of whether to serotest or vaccinate presumptively. Varicella seroprevalence among 7- to 12-year-old children with negative or uncertain histories has not previously been studied. Our main objective was to describe varicella seroprevalence among children ages 7 to 12 years with a negative or uncertain history of chickenpox.
  
  
  METHODS
  This was a cross-sectional study of children whose clinicians had ordered varicella serotesting. Guidelines from the medical group's regional pediatric infectious disease specialists recommended obtaining varicella serology on all children 7 to 12 years old with a negative or uncertain history. Parents were interviewed by telephone about the child's history of chickenpox before test results were completed.
  
  
  RESULTS
  Varicella seroprevalence ranged from 9% among 7-year-olds whose parents said they had definitely not had chickenpox to 68% among 11-year-olds whose parents were not sure whether they had had chickenpox. Among children whose parents were uncertain about their chickenpox history, almost one-half (48%) were seropositive. Twenty-five percent of children whose parents said they definitely had not and 32% of children whose parents said they had probably not had chickenpox were seropositive. Of parents whose children had experienced serotesting, 73% said they would prefer to have the blood test first rather than presumptive vaccination. For a large health maintenance organization, it was projected to be most cost-effective (in terms of cost per chickenpox case prevented) to recommend testing for children 9 to 12 years old with uncertain histories of chickenpox.
  
  
  CONCLUSIONS
  We conclude that among children 7 to 12 years old with negative or uncertain histories of chickenpox, varicella seroprevalence ranges from 9 to 68% depending on age and clinical history. Parents are generally receptive to serotesting, although individual preferences vary. In the population we studied it would be most cost-effective to recommend testing before deciding about vaccination for children 9 to 12 years old with uncertain histories of chickenpox.
authors.affiliation: Division of Research, Pediatric Vaccine Study Center, Kaiser Permanente, Oakland, CA 94611, USA. tal@dor.kaiser.org
authors.forename: T A
authors.initials: TA
authors.lastname: Lieu
authors.forename: S B
authors.initials: SB
authors.lastname: Black
authors.forename: H
authors.initials: H
authors.lastname: Takahashi
authors.forename: P
authors.initials: P
authors.lastname: Ray
authors.forename: A M
authors.initials: AM
authors.lastname: Capra
authors.forename: H R
authors.initials: HR
authors.lastname: Shinefield
authors.forename: N E
authors.initials: NE
authors.lastname: Adler
mesh_terms: D002644:Chickenpox / Q000191:economics / Q000453:epidemiology / Q000276:immunology*; D019433:Chickenpox Vaccine / Q000008:administration & dosage / Q000191:economics; D002648:Child; D003362:Cost-Benefit Analysis; D003430:Cross-Sectional Studies; D006279:Health Maintenance Organizations / Q000191:economics; D014645:Herpesvirus 3, Human / Q000276:immunology*; D006801:Humans; D016015:Logistic Models; D008487:Medical History Taking; D016036:Seroepidemiologic Studies; D012698:Serologic Tests / Q000191:economics*; D014611:Vaccination / Q000191:economics
chemical_list: D019433:Chickenpox Vaccine