Comparison 1. HCWs offered vaccination versus HCWs offered no vaccination: experimental design; data for periods of high influenza activity (three C‐RCTs; Carman 2000 and Potter 1997 152 days; Lemaitre 2009 118 days).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Influenza	2	752	Risk Difference (M‐H, Random, 95% CI)	‐0.00 [‐0.03, 0.03]
1.1 Unvaccinated residents	1	225	Risk Difference (M‐H, Random, 95% CI)	0.01 [‐0.03, 0.05]
1.2 Vaccinated and unvaccinated residents	1	527	Risk Difference (M‐H, Random, 95% CI)	‐0.01 [‐0.05, 0.03]
2 Lower respiratory tract infection	1	1059	Risk Difference (M‐H, Random, 95% CI)	‐0.02 [‐0.04, 0.01]
2.1 Vaccinated residents	1	538	Risk Difference (M‐H, Random, 95% CI)	‐0.02 [‐0.05, 0.01]
2.2 Unvaccinated residents	1	521	Risk Difference (M‐H, Random, 95% CI)	‐0.02 [‐0.06, 0.03]
3 Admission to hospital for respiratory illness	1		Risk Difference (M‐H, Random, 95% CI)	Totals not selected
3.1 Vaccinated and unvaccinated residents	1		Risk Difference (M‐H, Random, 95% CI)	0.0 [0.0, 0.0]
4 Deaths from influenza or its complications	2		Risk Difference (M‐H, Random, 95% CI)	Totals not selected
4.1 Vaccinated residents	1		Risk Difference (M‐H, Random, 95% CI)	0.0 [0.0, 0.0]
4.2 Unvaccinated residents	1		Risk Difference (M‐H, Random, 95% CI)	0.0 [0.0, 0.0]
4.3 Vaccinated and unvaccinated residents	1		Risk Difference (M‐H, Random, 95% CI)	0.0 [0.0, 0.0]
5 Death from any cause	4		Risk Difference (M‐H, Fixed, 95% CI)	Totals not selected
5.1 Vaccinated residents	1		Risk Difference (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
5.2 Unvaccinated residents	1		Risk Difference (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
5.3 Vaccinated and unvaccinated residents	3		Risk Difference (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]