Table 2 Comparison of pH1N1-positive cases with matched hospital controls and test-negative controls, respectively: Analysis of vaccination status, underlying illness and other potential risk factors

Pandemic influenza vaccination 2009/10

23

0

40

15

0.2 (0–1.5)

0.13

24

0

117

6

0.5 (0–4.8)

0.62

Seasonal influenza vaccination 2009/10

23

26

39

23

1.3 (0.2-7.5)

0.99

24

25

117

31

0.8 (0.2-2.8)

0.95

Seasonal influenza vaccination 2008/09

23

26

40

25

1.1 (0.3-4.1)

1.0

24

25

111

19

3.4 (0.6-20.8)

0.21

Seasonal influenza vaccination 2007/08

23

22

40

20

1.2 (0.2-7.6)

1.00

24

21

110

16

2.4 (0.4-14.9)

0.45

Pneumococcal vaccine

20

20

35

11

2.3 (0.4-15.9)

0.49

21

24

103

13

3.4 (0.6-19.5)

0.19

Pandemic vaccine offered by employer

23

9

40

30

0.1 (0–1.1)

0.07

24

8

115

12

1.1 (0.1-6.7)

1.00

Any chronic underlying illness

23

70

40

63

1.7 (0.1-117.7)

1.0

24

67

119

66

1.5 (0.4-6.3)

0.72

Any chronic lung disease

23

43

40

23

2.2 (0.6-8.6)

0.27

24

42

118

34

2.2 (0.6-7.9)

0.25

COPD

23

22

40

3

7.9 (1.0-∞)

0.06

24

21

118

27

1.2 (0.3-5.2)

0.99

Asthma

23

26

40

15

1.8 (0.4-8.9)

0.58

24

25

118

16

1.4 (0.3-5.5)

0.77

Chronic bronchitis

23

13

40

5

3.2 (0.2-177.0)

0.61

24

13

118

17

0.9 (0.1-4.5)

1.00

Cardiovascular disease

23

39

40

28

2.6 (0.4-29.2)

0.44

24

38

119

40

1.4 (0.3-5.6)

0.84

Immunosuppression

21

14

40

0

7.7 (0.8-∞)

0.07

22

14

116

15

1.1 (0.2-5.5)

1.00

BMI ≥31

23

30

39

8

5.1 (0.9-51.2)

0.06

24

29

118

17

2.3 (0.6-9.1)

0.27

Frailty

23

4

40

3

1.4 (0–117.7)

1.00

24

4

118

9

0.4 (0.1-3.4)

0.65

≥ 1 physician visits in past year

23

70

39

72^†

1.0 (0.3-3.3)

1.00

24

67

118

73^†

1.7 (0.5-6.6)

0.54

≥ 3 physician visits in past year

23

48

39

38^‡

1.5 (0.4-4.9)

0.64

24

46

118

53^‡

1.3 (0.4-4.2)

0.84

≥ 1 hospitalization in past year

23

17

39

49

0.2 (0–0.7)

0.01

24

17

119

32

0.4 (0.1-1.6)

0.26

Current smoker

23

61

40

53

1.3 (0.4-3.8)

0.81

24

58

119

40

1.6 (0.5-4.8)

0.53

>20 packyears vs. non-smoker

23

30

40

25

1.8 (0.4-11.1)

0.69

24

29

119

33

2.2 (0.4-14.4)

0.52

Alcohol: ≥ 1 drink/week

23

43

40

65

0.3 (0.1-1.1)

0.08

24

45

117

56

0.6 (0.2-1.8)

0.40

Children in household

23

39

40

15

4.3 (1.0-26.0)

0.04

24

38

119

36

1.0 (0.3-3.0)

1.00

Public transport (> = 3x/week) vs. none

23

30

40

58

0.2 (0–1.1)

0.06

24

29

119

45

0.3 (0.1-1.0)

0.06

Owns car

23

74

40

45

3.3 (1.0-14.3)

0.06

24

75

119

51

3.6 (1.1-13.9)

0.04

Completion of at least Grade 10

23

68

40

77

0.6 (0.1-3.1)

0.72

24

71

117

69

1.5 (0.5-5.4)

0.66

Private health insurance

23

24

40

13

2.1 (0.2-26.2)

0.74

24

25

119

17

1.2 (0.3-4.2)

1.00