Influenza (flu) is a highly contagious viral infection that is one of the most severe illnesses of the winter season. Influenza is spread easily from person to person, usually when an infected person coughs or sneezes.
Pneumonia is a serious infection or inflammation of the lungs. The air sacs fill with pus and other liquid, blocking oxygen from reaching the bloodstream. If there is too little oxygen in the blood, the body's cells cannot work properly, which can lead to death.
Influenza is a common cause of pneumonia, especially among younger children, the elderly, pregnant women, or those with certain chronic health conditions or who live in a nursing home. Most cases of flu never lead to pneumonia, but those that do tend to be more severe and deadly. In fact, flu and pneumonia were the eighth leading cause of death in the United States in 2016.
For both influenza and some types of pneumonia there are protective vaccines, although none are 100 percent protective. As flu strains change each year, it is necessary to get a flu vaccination each season to make sure you are protected against the most current strains. Pneumonia vaccinations are usually only necessary once, although a booster vaccination may be recommended for some individuals. Ask your healthcare provider if you are up to date on your vaccinations and to determine if any additional vaccinations are right for you.
Reviewed and approved by the American Lung Association Scientific and Medical Editorial Review Panel.
Page last updated: November 17, 2022