A pneumonia vaccine seems to save the lives of older adults who become so ill that they are hospitalized, even if does not prevent them from getting pneumonia, researchers said on Wednesday.

A study in several U.S. states showed that hospital patients who had been vaccinated were 40 to 70 percent less likely to die than unvaccinated patients, or those who could not remember whether they had been vaccinated.

The vaccinated patients had a lower risk of respiratory failure, kidney failure, heart attack or other complications, Dr. David Fisman of Princeton University in New Jersey and colleagues found.

Vaccinated patients also spent an average of two fewer days in the hospital, they will report in next week’s issue of Clinical Infectious Diseases.

“When people hit the door really sick and most likely to die, even in those people, being vaccinated was associated with a lower risk of death,” Fisman said in a statement.

Giving adults a vaccine against pneumococcal bacteria has been controversial, Fisman said in a statement, although the Centers for Disease Control and Prevention recommends it once every five years for everyone over 65.

“It’s been very hard to show that it prevents pneumonia, especially in older adults,” Fisman said. “Whether or not it prevents pneumonia is almost irrelevant - clearly it has an effect on reducing death in the individuals who get pneumonia.”

The vaccine for pneumonia does not provide complete protection against the disease, especially in older adults with weak immune systems. But it impairs bacterial infection of the blood. “Even if you’re really sick, prevention of the bacteria getting into the bloodstream ... might save your life,” Fisman said.

Fisman and colleagues in Pennsylvania and Texas analyzed data from nearly 63,000 patients hospitalized for pneumonia between 1999 and 2003. Twelve percent of the patients were known to have received pneumococcal vaccination, 23 percent were unvaccinated, and the rest had unknown vaccine status.

Pneumonia is an inflammation of the lungs that can be caused by several different bacteria, viruses or even inhaling bits of water or food. It can be complicated by additional bacterial infections.