Comparison 16. 1968 to 1969 pandemic: inactivated monovalent aerosol influenza vaccine versus placebo.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Influenza‐like illness	2	1009	Risk Ratio (M‐H, Random, 95% CI)	0.54 [0.32, 0.91]
1.1 Inactivated monovalent aerosol vaccine versus placebo ‐ matching ‐ 1 dose	2	650	Risk Ratio (M‐H, Random, 95% CI)	0.49 [0.17, 1.41]
1.2 Inactivated monovalent aerosol vaccine versus placebo ‐ matching ‐ 2 doses	1	359	Risk Ratio (M‐H, Random, 95% CI)	0.57 [0.38, 0.86]