Pneumonia is a fairly common complication of the flu, sometimes resulting in hospitalization. Might getting a flu vaccine make that a less likely scenario?

THIS STUDY analyzed data on 2,767 American children and adults who had been hospitalized with pneumonia, including about 6 percent who had also tested positive for the flu.

None had been hospitalized recently for any other reason, and none lived in a chronic-care facility or had severely weakened immune systems. Most people with flu-related pneumonia had not gotten a flu shot. The study found that people who developed pneumonia as a flu complication were 57 percent less likely to have been vaccinated against the flu than were people who did not have flu-related pneumonia.

WHO MAY BE AFFECTED? U.S. residents 6 months and older. Current recommendations are for nearly all people in that age range to get a flu vaccine each year. The flu vaccine does not guarantee protection against the various strains of influenza, but it is considered the best way to reduce the odds of getting the infectious respiratory virus and spreading it to others.

Although most people recover from the flu on their own in one to two weeks, it can lead not only to pneumonia but also to other complications, including bronchitis, sinus infection and ear infection. Severe complications can be life-threatening.

Centers for Disease Control and Prevention Director Dr. Tom Frieden, right, receives a flu shot from nurse B.K. Morris. (Jacquelyn Martin/AP)

CAVEATS The study did not include data on people with flu-related pneumonia who did not require hospitalization. The study suggests, but does not prove, that getting a flu shot prevents pneumonia. Ten of the study’s 19 authors received fees at some point from pharmaceutical companies that may have been involved with vaccines.

FIND THIS STUDY Oct. 13 issue of JAMA (www.jama.com; click on “All Issues”)

LEARN MORE ABOUT the flu at www.cdc.gov/flu. Learn about pneumonia at www.lung.org (click on “Lung Health & Diseases”)

The research described in Quick Study comes from credible, peer-reviewed journals.