Comparison 1.

Live vaccine versus placebo or no intervention (RCTs by age group)

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Influenza	6	9175	Risk Ratio (M‐H, Random, 95% CI)	0.20 [0.13, 0.32]
1.1 under 2 years	0	0	Risk Ratio (M‐H, Random, 95% CI)	0.0 [0.0, 0.0]
1.2 under 6 years	6	9115	Risk Ratio (M‐H, Random, 95% CI)	0.18 [0.11, 0.29]
1.3 over 6 years	1	60	Risk Ratio (M‐H, Random, 95% CI)	0.47 [0.23, 0.97]
2 Influenza‐like illness	8	188418	Risk Ratio (M‐H, Random, 95% CI)	0.67 [0.62, 0.72]
2.1 under 2 years	0	0	Risk Ratio (M‐H, Random, 95% CI)	0.0 [0.0, 0.0]
2.2 under 6 years	5	38646	Risk Ratio (M‐H, Random, 95% CI)	0.67 [0.57, 0.77]
2.3 over 6 years	8	149772	Risk Ratio (M‐H, Random, 95% CI)	0.67 [0.60, 0.74]