title: Polio extraimmunization in children younger than 2 years after changes in immunization recommendations.
abstract: OBJECTIVE
  To investigate trends over time in polio extraimmunization among children in 4 large health maintenance organizations and to study the association with recent changes in polio immunization policy.
  
  
  METHODS
  Using 176 169 children who were born after 1994 and enrolled for their first 2 years of life, we assessed rates and trends of polio extraimmunization in the Vaccine Safety Datalink project. We used logistic regression to test the association of extraimmunization with different polio immunization schedules and with sociodemographic characteristics and used Poisson regression to test changes in rates over time.
  
  
  RESULTS
  Overall, 10.5% were extraimmunized for poliovirus; children on the all inactivated polio virus or sequential schedule were one half as likely as those on the all oral polio virus schedule to be extraimmunized by 2 years of age. There was a significant decrease in extraimmunization over time, with <5% of children born at the end of 1997 being extraimmunized, compared with >15% at the beginning of 1994.
  
  
  CONCLUSIONS
  Poliovirus extraimmunization rates have fallen dramatically in association with the change-over to the all inactivated polio virus schedule.
authors.affiliation: Center for Health Studies, Group Health Cooperative, Seattle, Washington, USA.
authors.forename: Loren K
authors.initials: LK
authors.lastname: Mell
authors.forename: Robert L
authors.initials: RL
authors.lastname: Davis
authors.forename: John P
authors.initials: JP
authors.lastname: Mullooly
authors.forename: Steven B
authors.initials: SB
authors.lastname: Black
authors.forename: Henry R
authors.initials: HR
authors.lastname: Shinefield
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Zangwill
authors.forename: Joel I
authors.initials: JI
authors.lastname: Ward
authors.forename: S Michael
authors.initials: SM
authors.lastname: Marcy
authors.forename: Robert T
authors.initials: RT
authors.lastname: Chen
mesh_terms: D000284:Administration, Oral; D002675:Child, Preschool; D005260:Female; D006279:Health Maintenance Organizations / Q000706:statistics & numerical data; D006287:Health Planning Guidelines; D006801:Humans; D017589:Immunization Programs / Q000706:statistics & numerical data / Q000639:trends*; D007115:Immunization Schedule; D007117:Immunization, Secondary / Q000706:statistics & numerical data / Q000639:trends*; D007223:Infant; D016015:Logistic Models; D008297:Male; D011051:Poliomyelitis / Q000517:prevention & control; D017955:Poliovirus / Q000276:immunology; D011054:Poliovirus Vaccine, Inactivated / Q000008:administration & dosage; D011055:Poliovirus Vaccine, Oral / Q000008:administration & dosage; D023321:Poliovirus Vaccines / Q000008:administration & dosage*; D044469:Racial Groups; D012044:Regression Analysis; D012959:Socioeconomic Factors
chemical_list: D011054:Poliovirus Vaccine, Inactivated; D011055:Poliovirus Vaccine, Oral; D023321:Poliovirus Vaccines