Table 2. Risk of RSV associated LRTI, severe LRTI and hospitalisation, by age group and infection history, in a birth cohort from Kilifi District, Kenya.

		LRTI		Severe-LRTI		Admitted
Age group (months)	Infections	Number	Risk %	Number	Risk %	Number	Risk %	cyo
Primary infection
0-2	68	34	50.0	24	35.3	2	2.9	128
3-5	16	9	56.3	6	37.5	2	12.5	121
6-8	19	7	36.8	6	31.6	1	5.3	124
9-11	77	22	28.6	13	16.9	1	1.3	109
12-17	53	21	39.6	7	13.2	3	5.7	158
18-23	60	14	23.3	2	3.3	0	0.0	133
24+	33	7	21.2	1	3.0	0	0.0	52
total	326	114	35.0	59	18.1	9	2.8	827
Repeat infection
0-5	6	4	66.7	1	16.7	0	0.0	25
6-11	9	0	0.0	0	0.0	0	0.0	54
12-17	5	0	0.0	0	0.0	0	0.0	98
18-23	39	7	17.9	2	5.1	1	2.6	110
24-30	24	9	37.5	4	16.7	1	4.2	74
total	83	20	24.1	7	8.4	2	2.4	361

Notes.

Cases of severe LRTI are nested within LRTI cases

Fisher's Exact test by age for primary infection : LRTI P=0.002, severe-LRTI P<0.001, admissions P=0.063

Trend with age statistic (z) for primary infection: LRTI −3.68, P<0.001; severe-LRTI −5.72, P<0.001

Fisher's Exact test by age for repeat infection: LRTI P=0.01; severe-LRTI P= 0.410, admissions P=1.00

Trend with age statistic (z) for repeat infection: LRTI −0.3, P<0.761

Fisher's Exact test by infection history (Ha: primary > reinfection; 1 tail): LRTI P=0.038; severe-LRTI P=0.020; admissions P=0.608