Antibody response to respiratory syncytial virus infection in children <18 months old

Figures & data

Table 1. Characteristics of the cohort of 89 children.

				Unadjusted model^a			Adjusted model^b
Predictor variable	Overall (n=89)n (%)	RSV- (n=54)n (%)	RSV+ (n=35)n (%)	OR	95% CI	p-value	OR	95% CI	p-value
Gender
Females	39 (44)	28 (52)	11 (31)	Ref.
Males	50 (56)	26 (48)	24 (69)	2.3	(1.0, 5.7)	0.06	2.1	(0.9, 5.4)	0.10
Age at enrolment
0–4 mo	29 (33)	24 (44)	5 (14)	Ref.
5–8 mo	30 (34)	17 (31)	13 (37)	3.7	(1.1, 12.2)	0.03	7.7	(1.5, 38.9)	0.01
9–16 mo	30 (34)	13 (24)	17 (49)	6.3	(1.9, 20.9)	0.003	16.3	(2.1, 126.9)	0.008
Birth date
<7 months	41 (46)	30 (55)	11 (31)	Ref.
≥7 months	48 (54)	24 (44)	24 (69)	2.7	(1.1, 6.7)	0.03	2.5	(1.0, 6.3)	0.04
Gestational age (weeks)	39.0 (1.3)	39.0 (1.2)	39.1 (1.3)	1.1	(0.8, 1.6)	0.47	1.1	(0.8, 1.6)	0.47
Exposure to passive smoke^*
No	63 (72)	39 (74)	24 (69)	Ref.
Yes	25 (28)	14 (26)	11 (31)	1.3	(0.5, 3.3)	0.61	1.2	(0.5, 3.3)	0.69
Siblings
No	54 (61)	37 (69)	17 (49)	Ref.
Yes	35 (39)	17 (31)	18 (51)	2.3	(1.0, 5.5)	0.06	2.3	(0.9, 5.8)	0.08
Breast-feeding
No	22 (25)	13 (24)	9 (26)	Ref.
Yes	67 (75)	41 (76)	26 (74)	0.9	(0.3, 2.4)	0.86	1.3	(0.4, 3.8)	0.62
Day-care attendance
No	68 (76)	48 (89)	20 (57)	Ref.
Yes	21 (24)	6 (11)	15 (43)	6.0	(2.0, 17.7)	0.001	5.5	(1.7, 18.5)	0.005
Allergies
No	83 (93)	50 (93)	33 (94)	Ref.
Yes	6 (7)	4 (7)	2 (6)	0.8	(0.1, 4.4)	0.76	1.1	(0.2, 7.1)	0.94
URTIs from birth
No	34 (38)	24 (44)	10 (29)	Ref.
Yes	55 (62)	31 (56)	25 (71)	2.0	(0.8, 5.0)	0.13	1.7	(0.7, 4.5)	0.27
LRTIs from birth
No	76 (85)	52 (96)	24 (69)	Ref.
Yes	13 (15)	2 (4)	11 (31)	11.9	(2.4, 58.0)	0.002	15.9	(2.8, 88.8)	0.002
Infections from birth
No	28 (31)	23 (43)	5 (14)	Ref.
Yes	61 (69)	31 (57)	30 (86)	4.5	(1.5, 13.2)	0.007	4.1	(1.3, 12.8)	0.002
Hospitalizations
No	82 (92)	50 (93)	32 (91)	Ref.
Yes	7 (8)	4 (7)	3 (9)	1.2	(0.2, 5.6)	0.84	1.0	(0.2, 5.0)	0.99
Antibiotics for respiratory infections^*
No	69 (78)	49 (92)	20 (57)	Ref.	(2.7, 31.1)	0.000	8.4	(2.4, 30.1)	0.001
Yes	19 (22)	4 (8)	15 (43)	9.2		4
Antibiotics for non-respiratory infections^*
No	81 (92)	49 (92)	32 (91)	Ref.
Yes	7 (8)	4 (8)	3 (9)	1.1	(0.2, 5.5)	0.86	1.0	(0.2, 4.9)	0.96

95% CI, 95% confidence interval; LRTIs, lower respiratory tract infections; OR, odds ratio; RSV, respiratory syncytial virus; URTIs, upper respiratory tract infections.

* Data on 88 children.

^a Logistic regression model.

^b Multiple logistic regression model including birth date and gender as predictors.

Table 2. Antibody response to RSV during the study period among 35 RSV-positive patients.

	GMT at V1 (SD), log2 units	GMT at V2 (SD), log2 units	GMT fold change, log2 units	95% CI of fold change, log2 units	p-value
Birth date
< 7 months	7.1 (1.5)	7.9 (1.1)	0.8	(−0.2, 1.9)	Ref.
≥ 7 months	5.3 (1.4)	9.2 (1.0)	3.9	(3.1, 4.6)	<0.001
Virus type
RSV A	5.7 (1.6)	8.8 (1.2)	3.1	(2.3, 4.0)	Ref.
RSV B	6.9 (1.5)	8.5 (1.1)	1.7	(−0.1, 3.4)	0.15
Viral load
< 1^6 (copies/mL)	6.5 (1.8)	8.8 (1.3)	2.2	(1.2, 3.3)	Ref.
≥ 1^6(copies/mL)	5.3 (1.3)	8.8 (1.1)	3.5	(2.5, 4.6)	0.11
Viral shedding
<15 days	5.6 (1.8)	8.6 (1.2)	3.0	(1.9, 4.1)	Ref.
≥15 days	6.2 (1.5)	8.9 (1.2)	2.7	(1.5, 3.8)	0.70
Symptoms
URTIs	6.3 (1.7)	9.1 (1.0)	2.7	(1.6, 3.9)	Ref.
LRTIs	5.5 (1.5)	8.5 (1.3)	3.0	(1.9, 4.1)	0.76

95% CI, 95% confidence interval; GMT, geometric mean titres; LRTIs, lower respiratory tract infections; RSV, respiratory syncytial virus; URTIs, upper respiratory tract infections.

Table 3. Analysis of fold change (FC) of neutralizing antibody titer to RSV from baseline among 35 RSV-positive patients.

Variable	FC < 4 (n=12)n (%)	FC ≥ 4 (n=22)n (%)	OR^a	95% CI^a	p-value^a	Adjusted OR^b	95% CI^b	p-value^b
Birth date
< 7 months	7 (58)	4 (18)	Ref.
≥ 7 months	5 (42)	18 (82)	6.3	(1.4, 33.9)	0.02
Virus type
RSV A	9 (75)	19 (86)	Ref.			Ref.
RSV B	3 (25)	3 (14)	0.5	(0.1, 3.0)	0.41	0.3	(0.0, 1.9)	0.19
Viral load
< 1^6 (copies/mL)	6 (50)	11 (52)	Ref.			Ref.
≥ 1^6(copies/mL)	6 (50)	10 (48)	0.9	(0.2, 3.8)	0.90	0.6	(0.1, 3.1)	0.56
Viral shedding
<15 days	6 (50)	10 (46)	Ref.			Ref.
≥15 days	6 (50)	12 (54)	1.2	(0.3. 4.9)	0.80	1.7	(0.3, 8.7)	0.50
Symptoms
URTIs	10 (83)	7 (32)	Ref.			Ref.
LRTIs	2 (17)	15 (68)	10.7	(2.1, 83.2)	0.01	11.1	(1.9, 107.8)	0.01

95% CI, 95% confidence interval; FC, fold change; LRTIs, lower respiratory tract infections; OR, odds ratio; RSV, respiratory syncytial virus; URTIs, upper respiratory tract infections.

^a In columns 4, 5, and 6, the odds ratios of the 4r-fold change between the 2 modalities of the variable of interest and the corresponding 95% CI and p-value are obtained by a simple logistic regression model.

^b In columns 7, 8, and 9, the adjusted OR of the 4-fold change between the 2 modalities of the variable of interest and the corresponding 95% CI and p-value are obtained by a multiple logistic regression model including birth date as an adjusting factor.

Table 4. Duration of shedding among 35 RSV-positive patients.

Variable	Median shedding duration in days (95% CI)	HR^a	95% CI^a	p-value^a	Adjusted HR^b	95% CI^b	p-value^b
Birth date
< 7 months	14 (13, 21)	Ref.
≥ 7 months	28 (15, 50)	2.3	(1.0, 5.3)	0.06
Virus type
RSV A	15 (14, 28)	Ref.			Ref.
RSV B	19 ( 7, 42)	1.1	(0.4, 2.8)	0.82	0.8	(0.3, 2.1)	0.66
Viral load
< 1^6 (copies/mL)	14 (9, 21)	Ref.			Ref.
≥ 1^6(copies/mL)	27 (14, 42)	0.5	(0.2, 1.0)	0.05	0.4	(0.2, 0.9)	0.03
Symptoms
URTI	14 ( 9, 28)	Ref.			Ref.
LRTI	21 (14,35)	0.7	(0.3, 1.3)	0.23	0.4	(0.2, 0.9)	0.03
Antibody titer increase between V1 and V2
<4-fold	15 ( 9, 35)	Ref.			Ref.
≥4 -fold	16 (14, 28)	1.1	(0.5, 2.3)	0.84	0.7	(0.3, 1.6)	0.41

95% CI, 95% confidence interval; GMT, geometric mean titres; LRTIs, lower respiratory tract infections; RSV, respiratory syncytial virus; URTIs, upper respiratory tract infections.

^a In columns 3, 4, and 5, the HRs of the shedding duration between the 2 modalities of the variable of interest and the corresponding 95% CI and p-value are obtained by a simple Cox regression model.

^b In columns 6, 7, and 8, the adjusted HRs of the shedding duration between the 2 modalities of the variable of interest and the corresponding 95% CI and p-value are obtained by a multiple Cox regression model including birth date as an adjusting factor.