The U.S. Food and Drug Administration (FDA) has expanded the use of the best-selling pneumonia vaccine Prevnar 13, its producer Pfizer Inc. revealed in a statement released on Tuesday.

The vaccine, which provides protection against 13 strains of the streptococcus pneumoniae bacteria that cause pneumonia and other diseases, has previously been granted approval for use by children between 6 and 17 years old and adults who are over 50 years old.

The new approval now greenlights the use of the vaccine in infants, young children and adults who are 18 years old or older.

Pneumococcal pneumonia, which occurs when the streptococcus pneumoniae infects the lungs, is the most common serious form of disease caused by the bacterium in adults. Its symptoms include fever and chills, difficulty breathing, cough and chest pain. Older adults may experience low alertness and confusion.

According to the U.S. Centers for Disease Control and Prevention (CDC), about five in 100 people with non-invasive pneumococcal pneumonia will die from it albeit the rate could be higher in elderly patients.

"This expanded age indication in adults 18 to 49 offers an important public health benefit as appropriate vaccination against S. pneumoniae is critical to reducing the risk of pneumococcal disease, including in those with immunocompromising conditions," said Pfizer Vaccines Chief Medical and Scientific Affairs Officer Luis Jodar in a statement.

The health regulators' decision is based on the results of a late stage study, which involved adults who had not been vaccinated against pneumonia previously.

The study published in the journal Vaccine in October 2015, compared the safety, tolerability and immunogenicity of the vaccine in adults who were between 18 and 49 years of age with adults who were between 60 and 64 years old, for whom use of the Prevnar vaccine was already approved.

The FDA's decision makes Prevnar the only pneumococcal vaccine approved in the United States for patients beginning at 6 weeks old through adulthood.

Common side effects of the vaccine in adults include pain, swelling, or redness at the injection site, limited arm movement, fatigue, vomiting, headache, muscle pain, joint pain, reduced appetite, chills, or rash.

In children age 6 weeks to 17 years, common side effects include tenderness, swelling, or redness at the injection site, irritability, reduced appetite, shorter or longer sleep, and fever.

The vaccine is part of the immunization program of over 100 countries worldwide.It has grossed an annual sales of $6.25 billion in 2015, higher by 40 percent from 2014, helping buoy Pfizer's revenue.

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