TABLE 1.

Percentages of individuals with a history of pertussis or coughing attacks during the last year, of individuals with pertussis or coughing attacks more than 1 year ago, and of individuals without pertussis or coughing attacks according to IgG antibody levels in the population-based study^a

Occurrence pertussis or coughing attack status	n	% Individuals with IgG concn of:
		<5 U/ml		5–9 U/ml		10–49 U/ml		50–99 U/ml		≥100 U/ml
		%	95% CIa	%	95% CI	%	95% CI	%	95% CI	%	95% CI
Yes, during last yearb	886	9.6	8.0–11.3	11.6	9.4–13.8	11.3	9.7–12.9	19.9	13.0–26.9	25.5	12.2–38.8
Yes, more than 1 year agoc	463	5.5	4.3–6.7	6.1	4.6–7.6	6.7	5.2–8.5	7.3	3.5–11.0	14.1	2.7–25.5
Nod	6,407	84.9	82.8–87.0	82.3	79.9–84.6	81.8	80.1–83.5	72.8	65.2–80.5	60.4	45.3–75.5
Total	7,756	100		100		100		100		100

^aCI, confidence interval. 

^bParticipants who reported that a physician diagnosed pertussis during the last year or participants who reported coughing attacks that had lasted for more than 2 weeks during the last year. Among the 886 individuals, 15 individuals reported pertussis, and 12 of these 15 individuals reported coughing attacks. 

^cParticipants who reported that a physician diagnosed pertussis more than 1 year ago or participants who reported coughing attacks that had lasted for more than 2 weeks more than 1 year ago. No pertussis was diagnosed and no coughing attacks were reported during the last year. Among the 473 individuals, 126 individuals reported pertussis, and 45 of these individuals reported coughing attacks. 

^dParticipants who did not report pertussis or coughing attacks during the last year or more than one year ago.