Dr. Keipp Talbot of Vanderbilt University Medical Center said the study found flu vaccination reduced the risk of flu-related hospitalization by 71.4 percent among adults of all ages and by 76.8 percent in study participants age 50 and older during the 2011-12 flu season.
"This study is reassuring in light of recent reports that flu vaccination can be less effective in older adults," Talbot, the study's lead author, said in a statement. "This study showed that the flu vaccine can offer significant protection against serious illness resulting in hospitalization for adults of all ages."
An earlier preliminary study found the seasonal flu was effective in only 9 percent of adults age 65 and older.
The Centers for Disease Control and Prevention said older adults should seek medical treatment right away if they do develop flu-like symptoms, regardless of whether or not they have been vaccinated against the flu.
"Older adults often delay seeking medical treatment, but this can lead to complications that can become serious," said Dr. Mark Thompson, a CDC flu expert who was a co-author of the study. "People often aren't aware that there are drugs called 'anti-virals' that can treat the flu if you do become sick with the flu."
The findings were published online in the journal Clinical Infectious Diseases.