The transmission of Bordetella pertussis to young infants: identifying close and casual contact sources Public Deposited

Downloadable Content

Download PDF
Last Modified
  • March 21, 2019
  • Wendelboe, Aaron Mark.
    • Affiliation: Gillings School of Global Public Health, Department of Epidemiology
  • Background: Pertussis is increasingly recognized as a public health concern among infants too young to be vaccinated despite widespread vaccination. Valid estimates of who infects young infants with Bordetella pertussis are unavailable because previous studies did not identify source cases for 47% to 60% of infant cases. Furthermore, the proportion of transmission due to casual contact among those with unidentified sources remains unknown. Methods: A prospective multi-center study was conducted of laboratory confirmed infant pertussis cases (aged ? 6 months) and their close contacts in France, Germany, the U.S. and Canada from February 2003 through September 2004. A comprehensive diagnostic evaluation was performed on all participants independent of symptoms. Complete case and multiple imputation (MI) analyses were used to address missing data among participants and non-participants. Source cases were identified and described by relationship to the infant, age, and household status. Results: The study population comprised 95 index cases and 460 contacts. The source of pertussis was identified for 66% and 69% of infants using MI and the complete case analysis, respectively. In the primary analysis, parents accounted for 55% of source cases, followed by siblings (16%), aunts/uncles (10%), friends/cousins (10%), grandparents (6%), and part-time caretakers (2%). The estimated distribution of source cases with close contact was robust to changes in the source case definition in sensitivity analyses. However, the proportion of transmission due to casual community contact was sensitive to changes in the incubation and infectious periods used in the source case definition, and sensitive to allowing transmission from those with asymptomatic laboratory confirmed infection, resulting in estimates ranging from 20% to 48%. Discussion: This study provides evidence that among infants for whom a source case was identified, household members were responsible for 76% to 83% of transmission of B. pertussis to this high-risk group. Also, transmission from casual community contact accounts for an appreciable proportion of transmission to young infants. Vaccinating adolescents and adults with close contact to infants may be an important strategy in reducing the incidence of infant pertussis if high coverage rates can be achieved.
Date of publication
Resource type
Rights statement
  • In Copyright
  • Van Rie, Annelies
Degree granting institution
  • University of North Carolina at Chapel Hill
  • Open access

This work has no parents.