Table 2.
Poisson Regression for Risk Factors for Pertussis in Infants
| Risk Factor | Nonpertussis Infants | Pertussis Infants | Unadjusted | ||
|---|---|---|---|---|---|
| (n = 3466) | (n = 17) | IRR | 95% CI | P Value | |
| Male Sex | 53% | 59% | 1.3 | 0.5 − 3.4 | .61 |
| Preterm (<37 weeks) | 12% | 24% | 2.2 | 0.7 − 6.6 | .18 |
| Low birth weight (<2500 grams) | 25% | 36% | 1.7 | 0.5 − 5.9 | .38 |
| Small for gestational age (IG) | 37% | 50% | 1.7 | 0.5 − 5.8 | .41 |
| Small for gestational age (A) | 48% | 55% | 1.3 | 0.4 − 4.3 | .65 |
| Breastfed in 1st hour | 35% | 38% | 1.1 | 0.4 − 3.0 | .86 |
| Primiparous | 42% | 59% | 2.0 | 0.8 − 5.2 | .16 |
| Pahadi ethnicity | 58% | 69% | 1.6 | 0.6 − 4.6 | .37 |
| Literate | 61% | 60% | 1.6 | 0.6 − 4.6 | .37 |
| Household size (mean) | 5 | 4 | 0.9 | 0.7 − 1.1 | .39 |
| SES score (mean) | 0.39 | 0.35 | 0.2 | 0.0 − 8.6 | .42 |
| Age (days) at first pertussis vaccination (mean) | 85 | 96 | 1.0 | 1.0 − 1.0 | .17 |
| 1st pertussis vaccination received by 6 months | 56% | 65% | 1.5 | 0.5 − 3.9 | .47 |
Abbreviations: A, Alexander standards; CI, confidence interval; IG, INTERGROWTH-21st standards; IRR, incidence rate ratios; SES, socioeconomic status.