Comparison 1. Live vaccine versus placebo (RCTs).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Influenza	7	7718	Risk Ratio (M‐H, Random, 95% CI)	0.22 [0.11, 0.41]
1.1 Live attenuated vaccines (1 dose)	6	4675	Risk Ratio (M‐H, Random, 95% CI)	0.28 [0.14, 0.55]
1.2 Live attenuated vaccines (2 doses)	2	3043	Risk Ratio (M‐H, Random, 95% CI)	0.11 [0.04, 0.26]
2 Influenza‐like illness	7	124606	Risk Ratio (M‐H, Random, 95% CI)	0.69 [0.60, 0.80]
2.1 Live attenuated vaccines (1 dose)	2	3306	Risk Ratio (M‐H, Random, 95% CI)	0.64 [0.18, 2.22]
2.2 Live attenuated vaccines (2 doses)	6	121300	Risk Ratio (M‐H, Random, 95% CI)	0.66 [0.57, 0.76]
3 Otitis media (all episodes)	2	2873	Risk Ratio (M‐H, Random, 95% CI)	0.98 [0.95, 1.01]
4 School absenteeism	1		Risk Ratio (M‐H, Random, 95% CI)	Totals not selected
5 Working days lost (number of events, parents)	2	2874	Risk Ratio (M‐H, Random, 95% CI)	0.69 [0.46, 1.03]
6 Drug prescriptions (number of events)	1	1784	Risk Ratio (M‐H, Random, 95% CI)	0.99 [0.87, 1.12]
7 Outpatients attendance for pneumonia and influenza	2	2874	Risk Ratio (M‐H, Random, 95% CI)	0.76 [0.59, 0.98]
8 Influenza‐like illness (clustering sensitivity analysis)	7	49666	Risk Ratio (M‐H, Random, 95% CI)	0.69 [0.59, 0.80]
8.1 Live attenuated vaccines (1 dose)	2	1746	Risk Ratio (M‐H, Random, 95% CI)	0.64 [0.18, 2.23]
8.2 Live attenuated vaccines (2 doses)	6	47920	Risk Ratio (M‐H, Random, 95% CI)	0.65 [0.56, 0.76]