Comparison 2. Live aerosol influenza vaccine versus placebo or 'do nothing'.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Influenza	9	11579	Risk Ratio (M‐H, Random, 95% CI)	0.47 [0.35, 0.62]
1.1 WHO recommended ‐ matching vaccine	4	6584	Risk Ratio (M‐H, Random, 95% CI)	0.55 [0.37, 0.82]
1.2 WHO recommended ‐ vaccine matching absent or unknown	3	4568	Risk Ratio (M‐H, Random, 95% CI)	0.43 [0.27, 0.68]
1.3 Non WHO recommended ‐ vaccine matching absent or unknown	2	427	Risk Ratio (M‐H, Random, 95% CI)	0.21 [0.08, 0.56]
2 Influenza‐like illness	6	12688	Risk Ratio (M‐H, Random, 95% CI)	0.90 [0.84, 0.96]
2.1 WHO recommended ‐ matching vaccine	2	4254	Risk Ratio (M‐H, Random, 95% CI)	0.92 [0.76, 1.12]
2.2 WHO recommended ‐ vaccine matching absent or unknown	3	8150	Risk Ratio (M‐H, Random, 95% CI)	0.89 [0.82, 0.97]
2.3 Non WHO recommended ‐ vaccine matching absent or unknown	1	284	Risk Ratio (M‐H, Random, 95% CI)	0.92 [0.73, 1.16]
3 Influenza cases (clinically defined without clear definition)	3	23900	Risk Ratio (M‐H, Random, 95% CI)	0.89 [0.71, 1.11]
3.1 WHO recommended ‐ matching vaccine	1	1931	Risk Ratio (M‐H, Random, 95% CI)	0.63 [0.49, 0.80]
3.2 WHO recommended ‐ vaccine matching absent or unknown	1	2082	Risk Ratio (M‐H, Random, 95% CI)	1.05 [0.88, 1.25]
3.3 Non WHO recommended ‐ vaccine matching absent or unknown	1	19887	Risk Ratio (M‐H, Random, 95% CI)	0.98 [0.92, 1.05]
4 Local harms	13		Risk Ratio (M‐H, Random, 95% CI)	Subtotals only
4.1 Local ‐ upper respiratory infection symptoms	6	496	Risk Ratio (M‐H, Random, 95% CI)	1.66 [1.22, 2.27]
4.2 Local ‐ cough	6	2401	Risk Ratio (M‐H, Random, 95% CI)	1.51 [1.08, 2.10]
4.3 Local ‐ coryza	2	4782	Risk Ratio (M‐H, Random, 95% CI)	1.56 [1.26, 1.94]
4.4 Local ‐ sore throat	7	6940	Risk Ratio (M‐H, Random, 95% CI)	1.66 [1.49, 1.86]
4.5 Local ‐ hoarseness	1	306	Risk Ratio (M‐H, Random, 95% CI)	1.21 [0.51, 2.83]
4.6 Local ‐ combined endpoint (any or highest symptom)	3	4921	Risk Ratio (M‐H, Random, 95% CI)	1.56 [1.31, 1.87]
5 Systemic harms	7		Risk Ratio (M‐H, Random, 95% CI)	Subtotals only
5.1 Systemic ‐ myalgia	4	1318	Risk Ratio (M‐H, Random, 95% CI)	2.47 [1.26, 4.85]
5.2 Systemic ‐ fever	4	1318	Risk Ratio (M‐H, Random, 95% CI)	1.01 [0.54, 1.92]
5.3 Systemic ‐ fatigue or indisposition	3	1018	Risk Ratio (M‐H, Random, 95% CI)	1.39 [0.93, 2.07]
5.4 Systemic ‐ headache	2	975	Risk Ratio (M‐H, Random, 95% CI)	1.54 [1.09, 2.18]
5.5 Systemic ‐ combined endpoint (any or highest symptom)	5	1018	Risk Ratio (M‐H, Random, 95% CI)	1.40 [0.82, 2.38]