Table 2.

Seroprevalence of diphtheria antibody, overall and by age group

Age group	4-category classification				2-category classification
	No protection (< 0.01 IU/mL)	Uncertain protection (0.01–0.099 IU/mL)	Immunization protection present (0.1–0.99 IU/mL)	Long-term immunization protection (> = 1.0 IU/mL)	Susceptible (< 0.1 IU/mL)	Protected (> = 0.1 IU/mL)
	n % (95% CI)	n % (95% CI)	n % (95% CI)	n % (95% CI)	n % (95% CI)	n % (95% CI)
Children (2–17 years)	8	379	504	125	387	629
	0.8 (0.4,1.6)	37.3 (34.4,40.3)	49.6 (46.5,52.7)	12.3 (10.4,14.5)	38.1 (35.2,41.1)	61.9 (58.9,64.8)
Adults (18–60 years)	70	1436	744	51	1506	795
	3.0 (2.4,3.8)	62.4 (60.4,64.4)	32.3 (30.5,34.3)	2.2 (1.7,2.9)	65.4 (63.5,67.4)	34.6 (32.6,36.5)
Overall	78	1815	1248	176	1893	1424
	2.4 (1.92.9	54.7 (53.0,56.4)	37.6 (36.0,39.3)	5.3 (4.6,6.1)	57.1 (55.4,58.7)	42.9 (41.3,44.6)