Table 2. Age-stratified carriage prevalence of Corynebacterium diphtheriae and seroprevalence of diphtheria toxoid IgG () in 2 districts, Quang Ngai Province, Vietnam*.

Group	Mean ± SD age, y	Total.	Seroprevalence, No. (%) 95% CI		Carriage prevalence, No. (%) 95% CI
Age group, y
<5	3.2 ± 1.36	269	108 (39.5) 22.7‒59.2		12 (4.50) 3.7‒5.5
6‒17	10.1 ± 3.17	332	120 (36.7) 29.4‒44.6		10 (2.5) 0.1‒47.5
18‒40	29.5 ± 5.61	513	283 (55.3) 42.8‒67.1		5 (1.0) 0.6‒1.7
41‒55	46.3 ± 4.30	102	64 (62.9) 60.9‒64.8		0 (0) NA
Total	20.0 ± 14.3	1,216	575 (51.4) 3.6‒59.1		27 (1.4) 0.4‒5.4
District
Tay Tra, by age group, y
<5	3.1 ± 1.42	125	41 (32.8) 25.1‒41.5		6 (4.8) 2.2‒10.3
6‒17	9.9 ± 3.09	171	59 (34.5) 27.8‒41.9		0 (0) NA
18‒40	29.7 ± 5.19	258	152 (58.9) 52.8‒64.8		3 (1.2) 0.4‒3.5)
41‒55	46.4 ± 4.69	50	31 (62.0) 47.9‒74.3		0 (0) NA
Total	20.0 ± 14.2	604	283 (50.6) 33.6‒67.5		9 (0.9) 0.2‒3.7
Son Ha, by age group, y
<5	3.2 ± 1.31	144	67 (46.5) 38.5‒54.7		6 (4.2) 1.9‒9.0
6‒17	10.4 ± 3.25	151	61 (40.4) 32.9‒48.4		10 (6.6) 3.6‒11.9
18‒40	29.4 ± 6.04	265	131 (49.4) 43.4‒55.4		2 (0.8) 0.2‒0.3
41‒55	46.2 ± 3.94	52	33 (63.5) 49.7‒75.3		0 (0) NA
Total	20.0 ± 14.4	612	292 (52.4) 39.1‒65.3)		18 (2.0) 0.3‒11.0

*Seroprevalence and carriage prevalence were weighted for overall groups. IgG cutoff >0.1 IU/mL. NA, not applicable.