The transmission of Bordetella pertussis to young infants: identifying close and casual contact sources
Bibliographic record
Abstract
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.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.003 | 0.014 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".