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Table 3 Characteristics of index cases analyzed to determine associations with having a casual contact source case.

From: Estimating the role of casual contact from the community in transmission of Bordetella pertussis to young infants

  Crude Fully Adjusted
Characteristic of infant index case RR 95%CI RR 95%CI
Time to diagnosis     
   < 13 days 1.00 (...) 1.00 (...)
   14–20 days 1.53 (0.64, 3.7) 1.22 (0.45, 3.3)
   21–27 days 0.59 (0.13, 2.7) 0.49 (0.10, 2.5)
   28+ days 1.92 (0.65, 5.7) 1.60 (0.40, 6.4)
Age     
   < 2 months 0.75 (0.28, 2.0) 0.52 (0.08, 3.3)
   2–3 months 0.98 (0.39, 2.5) 1.33 (0.43, 4.2)
   4–6 months 1.00 (...) 1.00 (...)
Male gender 1.10 (0.52, 2.3) 1.20 (0.55, 2.6)
Partially vaccinated 1.57 (0.74, 3.3) 0.59 (0.13, 2.7)
Household size 1.03 (0.87, 1.2) 1.07 (0.85, 1.3)
Non-household contact enrolled 0.93 (0.42, 2.0) 1.04 (0.41, 2.6)
Childcare outside the home 1.57 (0.48, 5.2) 1.68 (0.39, 7.2)
Adolescent in close contact 0.70 (0.31, 1.6) 0.45 (0.14, 1.4)
Hospitalized 0.55 (0.25, 1.1) 0.87 (0.30, 2.5)
Continent of residence     
   Europe 1.00 (...) 1.00 (...)
   North America 2.59 (0.91, 7.4) 3.29 (0.86, 12.7)