Table 2

Secondary attack ratios of qRT-PCR confirmed influenza infection and clinical influenza, intention-to-treat analysis

Confirmation of influenza infection

Control Group

Mask Group

Mask & Hygiene

Group

p-value§


n/n

SAR

(95% CI#)

n/n

SAR

(95% CI#)

n/n

SAR

(95% CI#)


RT-PCR*

All cases

19/82

23 (13-35)

6/69

9 (3-19)

10/67

15 (5-27)

0.18


Influenza A (H1N1) pdm09

13/56

23 (11-37)

6/58

10 (3-20)

4/50

8 (2-17)

0.16


Influenza B

6/26

23 (5-48)

0/11

0

6/17

35 (7-60)

0.22


Season 2009/2010

8/36

22 (10-35)

3/31

10 (0-26)

3/39

8 (0-18)

0.29


Season 2010/2011

11/46

24 (9-42)

3/38

8 (0-19)

7/28

25 (4-45)

0.27


Implementation of intervention < 36 h after symptom onset of index patient

5/22

23 (6-39)

1/14

7 (0-23)

1/24

4 (0-16)

0.17


Clinical (ILI**)

All cases

14/82

17 (7-29)

6/69

9 (3-17)

6/67

9 (3-16)

0.37


Influenza A (H1N1) pdm09

10/56

18 (7-31)

6/58

10 (3-20)

3/50

6 (0-13)

0.29


Influenza B

4/26

15 (0-39)

0/11

0

3/17

18 (0-37)

0.56


Season 2009/2010

6/36

17 (6-31)

4/31

13 (3-30)

3/39

8 (0-16)

0.57


Season 2010/2011

8/46

17 (2-35)

2/38

5 (0-14)

3/28

11 (0-25)

0.48


Implementation of intervention < 36 h after symptom onset of index patient

4/22

18 (4-38)

2/14

14 (0-36)

1/24

4 (0-13)

0.41


*RT-PCR Real time polymerase chain reaction. **ILI Influenza-like-illness. §p-values adjusted for cluster design of the study

#95% CI 95% confidence interval. Confidence intervals were calculated using bootstrapping methods

Suess et al. BMC Infectious Diseases 2012 12:26   doi:10.1186/1471-2334-12-26

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