Getting a flu shot can help prevent influenza. But now, a large study in Britain indicates that older adults who get an annual flu vaccination are less likely to suffer a heart attack. _________________________________, age 40 and older. Researcher Niroshan Siriwardena of Britain's University of Lincoln led the study.

 

"Our research suggests that flu shots are associated with a reduction in relative risk of heart attack in adults by about 19%." _________________________________. The results were mathematically adjusted to reflect the fact that _________________________________ are more likely to get a flu shot.
答案：

(1)The study involved more than 78,000 people
(2)The reduction was even higher, 21%, for people who got their vaccination early in the flu season
(3)people who are at higher risk for heart attack in the first place