Table 2 Pooled crude and adjusted odd ratios of influenza vaccine effectiveness (per outcome) during influenza-season and off-season in vaccinated vs. unvaccinated diabetic patients

0–17

0

–

–

0

–

–

0

–

–

18–64

Case–control studies

1

0.46 (0.11–1.89)

NA¹

1

0.76 (0.07–8.06)

NA¹

0

–

NA¹

Case–control studies

2

0.32 (0.19–0.54)

0%

3

0.42 (0.19–0.94)

77%

1

0.73 (0.65–0.83)

NA¹

Case–control studies

0

–

–

1

0.57 (0.46–0.72)

NA¹

1

0.88 (0.68–1.14)

NA¹

Cohort studies

1

0.76 (0.50–1.15)

NA¹

0

–

–

0

–

–

Case–control studies

0

–

–

1

0.99 (0.97–1.01)

NA¹

1

1.00 (0.90–1.12)

NA¹

≥65

Cohort studies

3

0.54 (0.37–0.79)

90%

2

0.62 (0.57–0.68)

0%

1

0.70 (0.37–1.31)

NA¹

Case–control studies

2

0.39 (0.35–0.43)

0%

2

0.44 (0.36–0.53)

0%

0

–

–

Cohort studies

1

0.83 (0.72–0.95)

NA¹

0

–

–

1

0.91 (0.71–1.17)

NA¹

Case–control studies

2

0.89 (0.81–0.98)

0%

3

0.77 (0.60–0.99)

94%

1

0.66 (0.59–0.74)

NA¹

Case–control studies

1

0.20 (0.07–0.61)

NA¹

1

0.55 (0.47–0.66)

NA¹

1

0.48 (0.32–0.70)

NA¹

Case–control studies

0

–

–

1

0.87 (0.84–0.90)

NA¹

1

0.82 (0.70–0.96)

NA¹

Not reported

Cohort studies

1

1.75 (0.10–32.68)

NA¹

0

–

–

0

–

–

Cohort studies

1

0.34 (0.02–5.85)

NA¹

0

–

–

0

–

–