Table 3.

Incidence of Respiratory Tract Infections and Antibody Concentrations in LRTI+ and LRTI− Infants at 6 Months of Life

	LRTI+		LRTI−
	Incidence of seroconversions at 6 months
Respiratory pathogen	N	Incidence (%)	N	Incidence (%)	p
Influenza A	69	3 (4.4)	103	5 (4.9)	.55
RSV	72	6 (8.3)	103	6 (5.8)	.53
PIV1	71	30 (42.3)	104	35 (33.7)	.11
PIV2	70	24 (34.3)	103	19 (18.5)	.14
PIV3	67	24 (35.8)	100	30 (30.0)	.55
PNC1	63	59 (93.7)	95	87 (91.6)	.68
PNC5	63	53 (84.1)	95	77 (81.1)	.41
PNC6B	63	56 (88.9)	95	79 (83.2)	.30
PNC14	63	57 (90.5)	95	83 (87.4)	.66

	Infant antibody concentration at 6 months (EU/mL)
	N	GMC (95% CI)	N	GMC (95% CI)
Influenza A	84	2.3 (1.6–3.2)	121	1.7 (1.1–2.4)	.33
RSV	86	1.5 (0.8–2.6)	119	0.5 (0.3–0.8)	.01
PIV1	84	1.1 (0.6–1.8)	120	0.5 (0.3–0.8)	.08
PIV2	84	0.2 (0.1–0.4)	120	0.1 (0.1–0.2)	.17
PIV3	82	1.3 (0.7–2.4)	118	0.7 (0.4–1.3)	.14
PNC1	78	0.7 (0.6–0.8)	110	0.6 (0.6–0.7)	.63
PNC5	78	0.7 (0.6–0.7)	110	0.7 (0.7–0.8)	.10
PNC6B	77	0.6 (0.5–0.6)	110	0.6 (0.5–0.7)	.88
PNC14	78	2.9 (2.6–3.2)	110	2.6 (2.4–2.9)	.53

Bolded p values indicate significant and marginal differences. To adjust for one-to-n matching, p values for antibody concentrations were calculated by linear mixed-effects models; p values for seroconversions were calculated by conditional logistic regression.

N, no. of children tested; Incidence, no. of children with seroconversion; %, no. of children with seroconversion/total no. of children.