title: Undervaccination with diphtheria, tetanus, and pertussis vaccine: National trends and association with pertussis risk in young children.
abstract: The high coverage for ≥3 pertussis vaccine doses among Taiwanese children might not imply timely vaccination. Recently, resurgence of pertussis and challenges with availability of DTaP-IPV-Hib prompted this study.
  
  
  
  In the 1996-2012 national birth cohort, we calculated the prevalence and days of undervaccination against pertussis by age 36 months. We also compared the odds of undervaccination in each laboratory-confirmed pertussis patient at ages 3-35 months with sex-, residence-, and age-matched controls from the general population, using conditional logistic regression.
  
  
  
  The prevalence of undervaccination was 60.6% (median 16 days) and decreasing (p < 0.0001). Among 145 cases and 2,900 controls, 58 (40.0%) and 721 (24.9%) were undervaccinated (OR 2.28, 95% CI 1.57-3.31). The attributable risk percent was 22.5% (95% CI 14.5-27.9).
  
  
  
  Undervaccination was decreasing. Approximately up to one-fifth pertussis cases in children aged 3-35 months could have been prevented with on-time vaccination.
authors.affiliation: a Taiwan Centers for Disease Control , Taipei , Taiwan.
authors.forename: Wan-Ting
authors.initials: WT
authors.lastname: Huang
authors.affiliation: a Taiwan Centers for Disease Control , Taipei , Taiwan.
authors.forename: Hui-Chen
authors.initials: HC
authors.lastname: Lin
authors.affiliation: a Taiwan Centers for Disease Control , Taipei , Taiwan.
authors.forename: Chin-Hui
authors.initials: CH
authors.lastname: Yang
mesh_terms: D002675:Child, Preschool; D022681:Diphtheria-Tetanus-acellular Pertussis Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D005260:Female; D006801:Humans; D007114:Immunization / Q000706:statistics & numerical data*; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D012189:Retrospective Studies; D012307:Risk Factors; D013624:Taiwan / Q000453:epidemiology; D014917:Whooping Cough / Q000453:epidemiology* / Q000517:prevention & control*
chemical_list: D022681:Diphtheria-Tetanus-acellular Pertussis Vaccines
keywords: Immunization schedules; Taiwan; pertussis; timeliness; undervaccination; vaccine shortage