Comparison 6. Influenza vaccines versus no vaccination: cohort studies in nursing homes.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
6.1 Influenza	8	1941	Risk Ratio (M‐H, Random, 95% CI)	0.65 [0.32, 1.29]
6.1.1 Outbreak ‐ vaccine matching	4	658	Risk Ratio (M‐H, Random, 95% CI)	1.04 [0.43, 2.51]
6.1.2 Outbreak ‐ vaccine matching absent or unknown	2	592	Risk Ratio (M‐H, Random, 95% CI)	0.47 [0.22, 1.04]
6.1.3 No outbreak ‐ vaccine matching	2	691	Risk Ratio (M‐H, Random, 95% CI)	0.23 [0.05, 1.03]
6.1.4 No outbreak ‐ vaccine matching absent or unknown	0	0	Risk Ratio (M‐H, Random, 95% CI)	Not estimable
6.2 Influenza‐like illness	26	12388	Risk Ratio (M‐H, Random, 95% CI)	0.76 [0.66, 0.88]
6.2.1 Outbreak ‐ vaccine matching (circulating strains)	16	5963	Risk Ratio (M‐H, Random, 95% CI)	0.77 [0.64, 0.94]
6.2.2 Outbreak ‐ vaccine matching absent or unknown	6	4096	Risk Ratio (M‐H, Random, 95% CI)	0.80 [0.60, 1.05]
6.2.3 No outbreak ‐ vaccine matching	4	2329	Risk Ratio (M‐H, Random, 95% CI)	0.67 [0.46, 0.98]
6.2.4 No outbreak ‐ vaccine matching absent or unknown	0	0	Risk Ratio (M‐H, Random, 95% CI)	Not estimable
6.3 Pneumonia	17	10274	Risk Ratio (M‐H, Random, 95% CI)	0.53 [0.43, 0.66]
6.3.1 Outbreak ‐ vaccine matching	8	4482	Risk Ratio (M‐H, Random, 95% CI)	0.54 [0.42, 0.70]
6.3.2 Outbreak ‐ vaccine matching absent or unknown	5	3991	Risk Ratio (M‐H, Random, 95% CI)	0.68 [0.39, 1.21]
6.3.3 No outbreak ‐ vaccine matching	0	0	Risk Ratio (M‐H, Random, 95% CI)	Not estimable
6.3.4 No outbreak ‐ matching absent or unknown	4	1801	Risk Ratio (M‐H, Random, 95% CI)	0.35 [0.18, 0.68]
6.4 Hospitalisation for influenza‐like illness or pneumonia	12	28032	Risk Ratio (M‐H, Random, 95% CI)	0.51 [0.32, 0.81]
6.4.1 Outbreak ‐ vaccine matching	8	2027	Risk Ratio (M‐H, Random, 95% CI)	0.55 [0.36, 0.84]
6.4.2 Outbreak ‐ vaccine matching absent or unknown	2	3301	Risk Ratio (M‐H, Random, 95% CI)	0.82 [0.43, 1.58]
6.4.3 No outbreak ‐ vaccine matching	2	22704	Risk Ratio (M‐H, Random, 95% CI)	0.32 [0.14, 0.76]
6.4.4 No outbreak ‐ vaccine matching absent or unknown	0	0	Risk Ratio (M‐H, Random, 95% CI)	Not estimable
6.5 Deaths from flu or pneumonia	27	32179	Risk Ratio (M‐H, Random, 95% CI)	0.46 [0.33, 0.63]
6.5.1 Outbreak ‐ vaccine matching	16	6127	Risk Ratio (M‐H, Random, 95% CI)	0.58 [0.41, 0.83]
6.5.2 Outbreak ‐ vaccine matching absent or unknown	4	1089	Risk Ratio (M‐H, Random, 95% CI)	0.34 [0.11, 1.02]
6.5.3 No outbreak ‐ vaccine matching	3	23162	Risk Ratio (M‐H, Random, 95% CI)	0.27 [0.09, 0.87]
6.5.4 No outbreak ‐ vaccine matching absent or unknown	4	1801	Risk Ratio (M‐H, Random, 95% CI)	0.30 [0.14, 0.67]
6.6 All deaths	1	305	Risk Ratio (M‐H, Random, 95% CI)	0.40 [0.21, 0.77]
6.6.1 Outbreak ‐ vaccine matching	1	305	Risk Ratio (M‐H, Random, 95% CI)	0.40 [0.21, 0.77]
6.6.2 Outbreak ‐ vaccine matching absent or unknown	0	0	Risk Ratio (M‐H, Random, 95% CI)	Not estimable
6.6.3 No outbreak ‐ vaccine matching	0	0	Risk Ratio (M‐H, Random, 95% CI)	Not estimable
6.6.4 No outbreak ‐ vaccine matching absent or unknown	0	0	Risk Ratio (M‐H, Random, 95% CI)	Not estimable
6.7 Influenza cases (clinically defined without clear definition)	7	24238	Risk Ratio (M‐H, Random, 95% CI)	0.52 [0.27, 1.02]
6.7.1 Outbreak ‐ vaccine matching	2	271	Risk Ratio (M‐H, Random, 95% CI)	0.70 [0.11, 4.56]
6.7.2 Outbreak ‐ vaccine matching absent or unknown	1	155	Risk Ratio (M‐H, Random, 95% CI)	0.23 [0.09, 0.59]
6.7.3 No outbreak ‐ vaccine matching	1	22462	Risk Ratio (M‐H, Random, 95% CI)	0.40 [0.35, 0.46]
6.7.4 No outbreak ‐ vaccine matching absent or unknown	3	1350	Risk Ratio (M‐H, Random, 95% CI)	0.72 [0.41, 1.28]