F2 and pertussis: In the Quang Ngai survey, having been diagnosed with pertussis (aOR, 17.43; 95% CI, 1.54–197.70), a persistent cough with paroxysms/whoop (aOR, 4.27; 95% CI, 1.07–17.00), and smoking (aOR, 2.21; 95% CI, 1.07–4.57) were associated with an anti-PT IgG of ≥62.5 IU/mL.