Although anyone at any age can get pneumonia, its severity is much worse among infants, young children, and older adults. To treat it, pharmaceutical company Pfizer developed a vaccine, called Prevnar 13, for children. It turns out that the vaccine can also be used to treat people ages 65 and up, according to the company’s latest drug trial.

Pneumonia is an infection either of one, or both, of the lungs, and can be caused by a wide range of germs, including bacteria, viruses, and fungi — in these there are various strains, too. One-third of pneumonia cases in the U.S. are caused by the flu virus each year, according to the American Lung Association. Among children under 5, the flu can weaken the immune system enough for pneumonia-causing germs to infect. Prevnar 13 was developed to protect these children from 13 of the most common strains of pneumococcal bacteria, including pneumococcal meningitis, which causes death in one out of 10 children with the infection.

Among older adults, the infection is also deadly. Its attacks are frequent and severe because of aging organs — especially the respiratory tract, immune system, and digestive tract — and the diseases that come with old age. Figuring that Prevnar 13 could also work for adults, the U.S. health regulator decided in 2011 to widen its approved use on the basis that it succeeded in a trial, Reuters reported. Hence, Pfizer conducted their latest study, called CAPiTA, which is considered to be one of the largest drug trials ever.

The study included over 85,000 patients, ages 65 and older, and tested the effectiveness of Prevnar 13 against pneumonia. The drug passed both its primary goal and its secondary goal of preventing a first episode of community-acquired pneumonia (passed through social contact rather than at a hospital) and first episode of vaccine-type pneumococcal disease, which is a blood stream infection, The Wall Street Journal reported. “Pneumococcal pneumonia is a significant cause of illness and death in adults around the world, and the potential to reduce the burden of this disease through direct vaccination of adults represents a meaningful public health benefit,” said Emilio A. Emini, senior vice president of Vaccine Research and Development at Pfizer, in a statement.

Based on these results, Emini said that the company would be looking to the U.S.’s regulatory administrations, as well as those around the world, to approve the drug for broader use. Prevnar is a huge source of income for Pfizer. Annual sales of the drug, along with those of an older version, Prevnar 7, total $4.4 billion. If the drug is approved for use in older adults, Pfizer could make as much as $300 million on it in 2015 alone, J.P. Morgan analyst Chris Schott told Reuters. All of that depends, however, on how well the study’s results are received when they’re presented at a medical meeting in India next month.