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

White British

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

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

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)