Although anyone can get pneumonia, it is more common in certain groups. Children younger than age 2 and people older than age 65 are most likely to develop it. Certain factors can also increase your risk of pneumonia, such as:
Having a weakened immune system. This is usually a problem for people who have HIV/AIDS or alcoholism, or have undergone an organ transplant, chemotherapy,  or long-term treatment with steroids or other immunosuppressant drugs.
Being hospitalized or being on a ventilator.
Having a chronic condition including asthma, chronic obstructive pulmonary disease (COPD), structural lung disease, and heart disease.
Smoking.