title: Parental Tdap boosters and infant pertussis: a case-control study.
abstract: BACKGROUND
  Although recommended for almost a decade, evidence for field effectiveness of vaccinating close adult contacts of newborn infants against pertussis ("cocooning") is lacking. We evaluated the impact of a government-funded cocoon program during a pertussis epidemic in New South Wales, Australia.
  
  
  METHODS
  We matched all New South Wales laboratory-confirmed pertussis cases aged <4 months with onset between April 1, 2009, to March 30, 2011 to controls from the state birth register by date of birth and area of residence. Parental vaccine receipt was by self-report, with a subset verified. Parents were considered "immunized" if vaccinated ≥4 weeks before case symptom onset. The effectiveness of parental immunization (versus neither vaccinated) was quantified as (1 - odds ratio) × 100%.
  
  
  RESULTS
  Case households had fewer immunized mothers (22% vs 32%) or fathers (20% vs 31%) but were more likely to include additional and older children. After adjustment, when both parents met our definition of immunized, risk of pertussis at<4 months of age was reduced by 51% (95% confidence interval 10% to 73%). Maternal vaccination prepregnancy and an immunized father reduced the risk by 51% (95% confidence interval 0% to 76%).
  
  
  CONCLUSIONS
  Timely parental pertussis boosters provided significant protection. Evidence of protection from maternal vaccination prepregnancy is biologically plausible, and more precise data on the magnitude and duration of this is important for future policy recommendations.
authors.affiliation: National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases, and Discipline of Paediatrics and Child Health, University of Sydney, Children's Hospital at Westmead, Westmead, Australia; helen.quinn@health.nsw.gov.au.
authors.forename: Helen E
authors.initials: HE
authors.lastname: Quinn
authors.affiliation: Telethon Institute for Child Health Research, University of Western Australia, Subiaco, Australia; Menzies School of Health Research, Charles Darwin University, Casuarina, Australia; and.
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Snelling
authors.affiliation: National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases, and.
authors.forename: Andrew
authors.initials: A
authors.lastname: Habig
authors.affiliation: National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases, and Discipline of Paediatrics and Child Health, University of Sydney, Children's Hospital at Westmead, Westmead, Australia;
authors.forename: Clayton
authors.initials: C
authors.lastname: Chiu
authors.affiliation: New South Wales Ministry of Health, North Sydney, Australia.
authors.forename: Paula J
authors.initials: PJ
authors.lastname: Spokes
authors.affiliation: National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases, and Discipline of Paediatrics and Child Health, University of Sydney, Children's Hospital at Westmead, Westmead, Australia;
authors.forename: Peter B
authors.initials: PB
authors.lastname: McIntyre
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D022681:Diphtheria-Tetanus-acellular Pertussis Vaccines / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D007115:Immunization Schedule; D007117:Immunization, Secondary / Q000639:trends*; D007223:Infant; D008297:Male; D009517:New South Wales / Q000453:epidemiology; D010290:Parents; D014917:Whooping Cough / Q000453:epidemiology* / Q000517:prevention & control*; D055815:Young Adult
chemical_list: D022681:Diphtheria-Tetanus-acellular Pertussis Vaccines
keywords: cocooning; effectiveness; immunisation; pertussis; vaccine