Comparison 13. 1968 to 1969 pandemic: inactivated polyvalent parenteral influenza vaccine versus placebo.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Influenza‐like illness	3	3065	Risk Ratio (M‐H, Random, 95% CI)	0.71 [0.57, 0.88]
1.1 Standard recommended parenteral ‐ non‐matching ‐ 1 dose	3	2715	Risk Ratio (M‐H, Random, 95% CI)	0.74 [0.57, 0.95]
1.2 Standard recommended parenteral ‐ non‐matching ‐ 2 doses	1	350	Risk Ratio (M‐H, Random, 95% CI)	0.66 [0.44, 0.98]
2 Influenza	1	2072	Risk Ratio (M‐H, Random, 95% CI)	0.47 [0.26, 0.87]
2.1 Standard recommended parenteral ‐ non‐matching	1	2072	Risk Ratio (M‐H, Random, 95% CI)	0.47 [0.26, 0.87]
3 Hospitalisations	1	2072	Risk Ratio (M‐H, Random, 95% CI)	0.83 [0.41, 1.68]
3.1 Standard recommended parenteral ‐ non‐matching	1	2072	Risk Ratio (M‐H, Random, 95% CI)	0.83 [0.41, 1.68]
4 Pneumonia	1	2072	Risk Ratio (M‐H, Random, 95% CI)	1.01 [0.14, 7.17]
4.1 Standard recommended parenteral ‐ non‐matching	1	2072	Risk Ratio (M‐H, Random, 95% CI)	1.01 [0.14, 7.17]