Rubella seroprevalence using residual samples from the South African measles surveillance program: a cross-sectional analytic study

Figures & data

Table 1. Demographic characteristics of samples included from 2016 through 2018 (N = 6216)

Variable	Category	n (%)
Sample collection year	2016	1332 (21.43)
	2017	2973 (47.83)
	2018	1911 (30.74)
Gender	Male	3211 (51.66)
	Female	2877 (46.28)
	Unknown	128 (2.06)
Province	Eastern Cape	511 (8.22)
	Free State	193 (3.11)
	Gauteng	1890 (30.42)
	KwaZulu-Natal	1029 (16.56)
	Limpopo	390 (6.28)
	Mpumalanga	674 (10.85)
	Northern Cape	274 (4.41)
	North West	372 (5.99)
	Western Cape	881 (14.18)
	Unknown	2 (0.03)
Age group	0 – 11 months	626 (10.07)
	1 to 5 y	2920 (46.98)
	6 to 10 y	1333 (21.44)
	11 to 15 y	340 (5.47)
	16 to 49 y	681 (10.96)
	≥50 y	278 (4.47)
	Unknown	38 (0.16)

Figure 1. Results of rubella IgG testing by age in years for records with known age (n=6021)

Figure 2. Proportion of rubella susceptible (IgG negative) individuals among males and females. Error bars represent 99% confidence intervals

Figure 3. Proportion of rubella susceptible (IgG negative) individuals in each age group among males and females

Figure 4. Proportion of rubella susceptible (IgG negative) individuals for each province. Error bars represent 99% confidence intervals

* WCP= Western Cape Province, KZP= KwaZulu-Natal Province, ECP= Eastern Cape Province, LP= Limpopo Province, NCP= Northern Cape Province, MP= Mpumalanga Province, FSP= Free State Province, GP= Gauteng Province, NWP= North West Province

Figure 5. Proportion of rubella susceptible (IgG negative) individuals by age group. Error bars represent 99% confidence intervals

Table 2. Unadjusted and adjusted logistic regression analyses

Variable	Rubella IgG result: n (%)		Unadjusted		Adjusted
	susceptible	Immune	OR (95% CI)	p- value	OR (95% CI)	p-value
Gender (n=5931)				<0.001		0.086
Male	1491 (53.31)	1306 (46.69)	Ref	Ref <0.001	0.95 (0.84 - 1.06)	Ref 0.41
Female	1853 (59.13)	1281 (40.87)	0.79 (0.71-0.87)
Province (n=6057)				<0.001		0.01
Eastern Cape	302 (60.76)	195 (39.24)	0.99 (0.79 - 1.24)	0.92 0.13 <0.001 0.98 0.51 0.03 0.31 <0.001 Ref	0.99 (0.77 - 1.28)	0.96
Free State	104 (55.03)	85 (44.97)	0.78 (0.57 – 1.07)		0.76 (0.53 - 1.08)	0.12
Gauteng	955 (52.39)	868 (47.61)	0.70 (0.59–0.83)		0.74 (0.62 - 0.89)	0.002
KwaZulu-Natal	618 (61.01)	395 (38.99)	0.99 (0.83 – 1.20)		0.93 (0.76 - 1.14)	0.48
Limpopo	225 (59.06)	156 (40.97)	0.92 (0.72 – 1.18)		0.82 (0.63 - 1.08)	0.15
Mpumalanga	369 (55.41)	297 (44.59)	0.79 (0.65 – 0.97)		0.77 (0.62 – 0.97)	0.03
Northern Cape	174 (48.07)	188 (51.93)	0.87 (0.66 – 1.14)		1.03 (0.76 – 1.41)	0.85
North West	156 (57.56)	115 (42.44)	0.59 (0.46– 0.76)		0.68 (0.52 – 0.90)	0.01
Western Cape	522 (61.05)	333 (38.95)	Ref			Ref
Age group (n=6021)				<0.001		<0.001
0 – 11 months	471 (81.91)	104 (18.09)	6.24 (4.52 – 8.63)	<0.001 <0.001 0.74 0.01 <0.001 Ref	6.20 (4.42 – 8.70)	<0.001
1 to 5 years	2050 (71.50)	817 (28.50)	3.46 (2.67 – 4.47)		3.44 (2.62 – 4.53)	<0.001
6 to 10 years	541 (40.95)	780 (59.05)	0.96 (0.73 – 1.25)		0.94 (0.70 – 1.25)	0.65
11 to 15 years	105 (31.25)	231 (68.75)	0.63 (0.45 – 0.88)		0.62 (0.43 – 0.88)	0.01
16 to 49 years	131 (19.91)	527 (80.09)	0.34 (0.25 – 0.47)		0.36 (0.26 – 0.49)	<0.001
> 50 years	111 (42.05)	153 (57.95)	Ref			Ref

*Rubella susceptibility (IgG negative) is the outcome variable with age, sex and province of origin as predictor variables.