A Systematic Review and Meta-Analysis of the Relationship between Receiving the Flu Vaccine with Acute Cerebrovascular Accident and Its Hospitalization in the Elderly

Table 4

Subgroup analysis of the association between receiving the flu vaccine with stroke and its hospitalization in the elderly.

Characteristics		Number of studies	OR (95% CI)	value	Heterogeneity
Study design	Cohort	6	0.85 (0.77-0.94)	0.017	63.8%
	Case-control	8	0.81 (0.70-0.93)	0.005	65.1%
Study location	North America	2	0.89 (0.60-1.32)	0.098	63.4%
	Europe	7	0.79 (0.69-0.91)	0.007	66.2%
	International	1	1.01 (0.88–1.17)	—	0.0
	Asia	4	0.83 (0.74-0.95)	0.061	59.2%
Average age	<70	9	0.85 (0.73-0.99)	≤0.001	73.2%
	≥70	5	0.82 (0.75-0.89)	0.095	49.4%
Follow up - time	Less than 5	13	0.84 (0.77-0.91)	≤0.001	68.6%
	More than 5	1	0.82 (0.67-1.00)	—	0.0%
Sample size	Less than 10,000	6	0.70 (0.49-1.01)	0.002	73.5%
	More than 10,000	8	0.84 (0.79-0.90)	0.007	63.7%
Quality assessment	Good quality	9	0.88 (0.81-0.95)	0.002	68.1%
	Medium quality	5	0.70 (0.58-0.85)	0.084	51.3%
Sex ratio (male to female)	Less than one	7	0.83 (0.75-0.91)	≤0.001	70.9%
	Equal or more than one	7	0.84 (0.72-0.97)	0.021	63.4%