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Table 4 Unadjusted and adjusted odds ratios for the association between age at VZV infection and exposure variables, stratified by ethnic group

From: Cytomegalovirus, Epstein-Barr virus and varicella zoster virus infection in the first two years of life: a cohort study in Bradford, UK

White British   Age at VZV infection Unadjusted OR
(95% CI)
Unadjusted OR
(95% CI)
n = 378
Adjusted OR
(95% CI)
n = 378
by 12 mths 12–24 mths uninfected at 24 mths
All children, n = 391 34 (9%) 90 (23%) 267 (68%)  
Birth order (391) 1 9 (5%) 27 (15%) 148 (80%) 1.0 1.0 1.0
2 19 (15%) 47 (37%) 62 (48%) 4.22 (2.58–6.91) 4.23 (2.56–6.97) 4.83 (2.68–8.70)
3+ 6 (8%) 16 (20%) 57 (72%) 1.60 (0.87–2.93) 1.55 (0.83–2.87) 2.24 (0.92–5.49)
Total household members at 12 m (389) median
IQR, range
4
3–4, 2–5
4
3–4, 2–8
4
3–4, 2–8
1.06 (0.87–1.28) 1.06 (0.87–1.28) 0.89 (0.66–1.20)
No. of children (<16y) in household at 12 m (369) median
IQR, range
2
1–2, 1–4
2
1–2, 1–6
1
1–2, 1–5
1.26 (1.00–1.58)   -
Duration of breastfeeding (390) never 8 (8%) 21 (21%) 73 (72%) 1.0 1.0 1.0
<=4 weeks 4 (4%) 21 (21%) 74 (75%) 0.82 (0.44–1.52) 0.83 (0.44–1.56) 0.88 (0.45–1.72)
1–6 months 11 (12%) 22 (23%) 62 (65%) 1.37 (0.76–2.49) 1.45 (0.79–2.68) 1.52 (0.78–2.95)
6–12 months 8 (12%) 20 (31%) 37 (57%) 1.87 (0.99–3.53) 1.98 (1.04–3.79) 2.05 (0.98–4.31)
>12 months 3 (10%) 6 (21%) 20 (69%) 1.16 (0.48–2.82) 1.20 (0.49–2.94) 0.99 (0.38–2.56)
Bedroom sharing in first year (389) no 21 (9%) 50 (23%) 149 (68%) 1.0   -
yes 13 (8%) 38 (22%) 118 (70%) 0.89 (0.58–1.37)   -
Bedroom sharing in second year (391) No 20 (8%) 54 (22%) 174 (70%) 1.0 1.0 1.0
yes 14 (10%) 36 (25%) 93 (65%) 1.26 (0.82–1.94) 1.25 (0.81–1.93) 1.11 (0.66–1.85)
Bed sharing in second year (391) No 31 (8%) 83 (23%) 250 (69%) 1.0   -
yes 3 (11%) 7 (26%) 17 (63%) 1.30 (0.59–2.87)   -
Formal child care up to 12 m visit (total hours) (381) No childcare 13 (8%) 35 (22%) 113 (70%) 1.0 1.0 1.0
<1165 total hours 2 (6%) 9 (26%) 23 (68%) 1.08 (0.49–2.35) 1.08 (0.49–2.36) 0.94 (0.40–2.19)
> = 1165 total hours 14 (15%) 28 (29%) 53 (56%) 1.90 (0.13–3.18) 1.90 (1.13–3.18) 1.69 (0.92–3.11)
No formal (only informal) 4 (4%) 16 (18%) 71 (78%) 0.65 (0.36–1.18) 0.65 (0.36–1.19) 0.66 (0.34–1.26)
Mother and baby activities in first year (389) Rarely 16 (7%) 44 (21%) 149 (71%) 1.0   -
At least once a month 18 (10%) 44 (24%) 118 (66%) 1.31 (0.86–2.00)   -
Mother and baby activities in second year (389) Rarely 18 (11%) 32 (20%) 108 (68%) 1.0 1.0 1.0
At least once a month 16 (7%) 57 (25%) 158 (68%) 0.94 (0.61–1.44) 0.91 (0.59–1.41) 0.75 (0.46–1.23)
Age 24 m blood sample taken (mths) (391) 23.59–24.99 7 (8%) 21 (25%) 56 (67%) 1.0 1.0 1.0
25–26.99 20 (9%) 49 (21%) 159 (70%) 0.89 (0.52–1.50) 0.87 (0.51–1.48) 0.68 (0.38–1.21)
27–32.89 7 (9%) 20 (25%) 52 (66%) 1.04 (0.55–1.97) 1.01 (0.53–1.92) 0.73 (0.37–1.47)
Pakistani   by 12 mths 12–24 mths uninfected at 24 mths Unadjusted OR
(95% CI)
Unadjusted OR
(95% CI)
n = 466
Adjusted OR
(95% CI)
n = 466
All children, n = 472 46 (10%) 65 (14%) 361 (76%)  
Birth order (472) 1 5 (4%) 12 (10%) 109 (87%) 1.0 1.0 1.0
2 13 (12%) 22 (21%) 72 (67%) 3.06 (1.61–5.83) 3.07 (1.61–5.86) 3.75 (1.89–7.43)
3+ 28 (12%) 31 (13%) 180 (75%) 2.17 (1.21–3.91) 2.16 (1.20–3.89) 3.05 (1.53–6.09)
Total household members at 12 m (468) median
IQR, range
6
5–7, 4–13
5
4–7, 3–11
6
5–7, 2–15
0.99 (0.90–1.09) 0.99 (0.90–1.09) 0.98 (0.88–1.09)
No. of children (<16y) in household at 12 m (456) median
IQR, range
3
2–3, 1–5
3
2–4, 1–6
3
2–4, 1–8
1.06 (0.91–1.25) - -
Duration of breastfeeding (468) never 12 (14%) 11 (13%) 61 (73%) 1.0 1.0 1.0
<=4 weeks 6 (7%) 11 (12%) 74 (81%) 0.58 (0.29–1.18) 0.59 (0.29–1.20) 0.64 (0.31–1.35)
1–6 months 11 (9%) 15 (12%) 95 (79%) 0.70 (0.37–1.34) 0.70 (0.37–1.34) 0.86 (0.44–1.66)
6–12 months 10 (9%) 16 (16%) 76 (75%) 0.87 (0.45–1.65) 0.88 (0.46–1.68) 1.03 (0.52–2.02)
>12 months 7 (10%) 11 (16%) 52 (74%) 0.88 (0.43–1.79) 0.88 (0.43–1.79) 0.97 (0.47–2.02)
Bedroom sharing in first year (468) no 2 (6%) 3 (10%) 26 (84%) 1.0 - -
yes 44 (10%) 61 (14%) 332 (76%) 1.64 (0.62–4.37)   -
Bedroom sharing in second year (472) no 3 (13%) 2 (8%) 19 (79%) 1.0 1.0 1.0
yes 43 (10%) 63 (14%) 342 (76%) 1.12 (0.41–3.05) 1.12 (0.41–3.07) 0.96 (0.33–2.79)
Bed sharing in second year (471) No 26 (10%) 35 (13%) 206 (77%) 1.0   -
yes 20 (10%) 30 (15%) 154 (75%) 1.09 (0.71–1.66)   -
Any regular child care arrangement up to 24 m visit (472) no 40 (11%) 54 (14%) 286 (75%) 1.0 1.0 1.0
yes 6 (7%) 11 (12%) 75 (81%) 0.68 (0.38–1.21) 0.64 (0.36–1.16) 0.78 (0.42–1.44)
Mother and baby activities in first year (468) Rarely 42 (10%) 56 (14%) 307 (76%) 1.0   -
At least once a month 4 (6%) 8 (13%) 51 (81%) 0.72 (0.37–1.40)   -
Mother and baby activities in second year (472) Rarely 23 (9%) 30 (12%) 200 (79%) 1.0 1.0 1.0
At least once a month 23 (10%) 35 (16%) 161 (74%) 1.34 (0.88–2.04) 1.37 (0.90–2.10) 1.43 (0.92–2.21)
Maternal age at recruitment (472) Mean, SD, range 28.0, 4.48
19–39
28.8, 5.23
19–41
28.9, 5.38
17–44
0.98 (0.95–1.02) 0.98 (0.94–1.02) 0.95 (0.90–0.99)
Age 24 m blood sample taken (mths) (472) 23.59–24.99 7 (8%) 12 (13%) 72 (79%) 1.0 1.0 1.0
25–26.99 20 (8%) 35 (15%) 185 (77%) 1.12 (0.63–2.01) 1.08 (0.60–1.94) 1.13 (0.62–2.08)
27–32.89 19 (13%) 18 (13%) 104 (74%) 1.41 (0.75–2.63) 1.39 (0.75–2.61) 1.42 (0.74–2.73)
  1. VZV varicella zoster virus; OR odds ratio; CI confidence interval; IQR inter-quartile range