Comparison 9. Influenza vaccines versus no vaccination: cohort studies in community ‐ adjusted rates.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
9.1 Hospitalisation for influenza or pneumonia	8		Odds Ratio (IV, Random, 95% CI)	0.73 [0.67, 0.79]
9.1.1 Epidemic ‐ vaccine matching	6		Odds Ratio (IV, Random, 95% CI)	0.71 [0.65, 0.77]
9.1.2 Non‐epidemic ‐ vaccine not matching	1		Odds Ratio (IV, Random, 95% CI)	0.90 [0.58, 1.38]
9.1.3 Epidemic year ‐ vaccine matching absent or unknown	1		Odds Ratio (IV, Random, 95% CI)	0.82 [0.68, 0.98]
9.2 Hospitalisation for any respiratory disease	13		Odds Ratio (IV, Random, 95% CI)	0.78 [0.72, 0.85]
9.2.1 Epidemic ‐ vaccine matching	9		Odds Ratio (IV, Random, 95% CI)	0.71 [0.67, 0.74]
9.2.2 Non‐epidemic ‐ vaccine not matching	2		Odds Ratio (IV, Random, 95% CI)	0.91 [0.76, 1.08]
9.2.3 Non‐epidemic year ‐ vaccine matching	2		Odds Ratio (IV, Random, 95% CI)	0.94 [0.84, 1.06]
9.3 Hospitalisation for heart disease	6		Odds Ratio (IV, Random, 95% CI)	0.76 [0.70, 0.82]
9.3.1 Epidemic year ‐ vaccine matching	5		Odds Ratio (IV, Random, 95% CI)	0.75 [0.70, 0.82]
9.3.2 Non‐epidemic ‐ vaccine not matching	1		Odds Ratio (IV, Random, 95% CI)	0.80 [0.55, 1.16]
9.4 All deaths	7		Odds Ratio (IV, Random, 95% CI)	0.53 [0.46, 0.61]
9.4.1 Epidemic year ‐ vaccine matching	5		Odds Ratio (IV, Random, 95% CI)	0.47 [0.42, 0.53]
9.4.2 Epidemic year ‐ vaccine matching absent or unknown	1		Odds Ratio (IV, Random, 95% CI)	0.65 [0.57, 0.75]
9.4.3 Non‐epidemic year ‐ vaccine matching	1		Odds Ratio (IV, Random, 95% CI)	0.76 [0.60, 0.97]
9.5 Combined outcome: all deaths or severe respiratory illness	1		Odds Ratio (IV, Random, 95% CI)	0.70 [0.37, 1.34]
9.5.1 Epidemic year ‐ vaccine matching	1		Odds Ratio (IV, Random, 95% CI)	0.70 [0.37, 1.34]