Table 3.

Case-control studies of influenza vaccine effectiveness (VE) for preventing pneumonia- or influenza-related hospitalization among community-dwelling elderly.

Author	Publication year	Country	Study period	Subject age (years)	Sample size	VE (95% CI)
Grijalva et al.24	2015	United States	2010–2012	≥65	429	48 (−33 to 80)
Mahmud et al.23	2015	Canada	2009–2010	≥65	5,852	10 (−16–30)
Jackson et al.28	2008	United States	2000–2003	≥65	3,519	9 (−10 to 23)
Crocetti et al.31	2001	Italy	1994–1995	≥65	825	33 (5 to 52)
Puig-Barbera et al.33	1997	Spain	1994–1995	≥65	249	79 (45 to 92)
Ohmit et al.34	1995	United States	1990–1991	≥65	2,197	31 (4 to 51)
			1991–1992		2,761	32 (7 to 50)
Mullooly et al.35	1994	United States	1981–1989	≥65, non-high-risk group	150,713	40 (1 to 64)
				≥65, high-risk group	100,321	30 (17 to 42)
Fedson et al.36	1993	United States	1982–1983	≥65	10,471	37 (15 to 53)
			1985–1986		9,720	39 (19 to 53)
Foster et al.37	1992	United States	1989–1990	≥65	2,507	33 (8 to 52)