Pneumococcal vaccine does not reduce pneumonia risk in the elderly, Group Health study finds

Seattle—The pneumococcal polysaccharide vaccine, recommended for all people over age 65, does notreduce the overall risk of pneumonia in seniors, according to a Group Health Cooperative study of 47,000 people published in the May 1 issue of The New England Journal of Medicine.

The study found that the vaccine is effective in preventing bloodstream infection with the pneumococcal bacterium, an infectious agent that can also infect the lungs, causing pneumonia. Although this bloodstream infection is relatively uncommon, it is the most serious form of pneumococcal infection and is fatal in about 20 percent of cases. The pneumococcal polysaccharide vaccine is still recommended for seniors in order to prevent this bloodstream infection.

Bloodstream infections represent just the tip of the iceberg of all pneumococcal infections. The most frequent type of pneumococcal infection in seniors is pneumonia. Approximately a third to a half of the estimated 350,000 to 620,000 hospitalizations for pneumonia each year among Americans aged 65 and older is caused by the pneumococcal bacterium. In the Group Health study, seniors who had received the pneumococcal polysaccharide vaccine were not less likely to contract pneumonia than seniors who had not been vaccinated. This suggests that the vaccine does not prevent pneumonia caused by the pneumococcal bacterium.

"These findings indicate the importance of research to find other ways to prevent the most common cause of pneumonia in the elderly," said Lisa Jackson, MD, MPH, associate investigator at Group Health Center for Health Studies, and the principal investigator of the study.

Health care providers should continue to vaccinate all people aged 65 and older because the vaccine prevents serious pneumococcal bloodstream infections, said Jackson. "But the medical community should be aware that the vaccine does not appear to alter the overall risk of pneumonia," she added.

Jackson also recommended that elderly people get their annual flu vaccine, because that shot can protect against pneumonia and other illness caused by the influenza virus.

How the study was conducted

Jackson and her colleagues accessed computerized medical information for some 47,000 Group Health members, aged 65 and older. Hospitalizations associated with a pneumonia diagnosis were confirmed by review of medical charts. Using those data, they determined whether people who had received pneumococcal vaccine were more or less likely to be hospitalized for pneumonia or to have received outpatient treatment for pneumonia over a three-year period. Additionally, lab records revealed how many vaccinated and unvaccinated people had pneumococcal bloodstream infection.

A previous study conducted by investigators from a Minneapolis HMO suggested the pneumococcal vaccine could reduce the risk of hospitalization for pneumonia in seniors with chronic lung disease. But that study involved just 1,800 patients and did not include all seniors. Group Health's study, which was larger and more thorough, indicates that the vaccine does not reduce pneumonia hospitalizations.

Implications for future research

Jackson said the findings have important implications for research into new pneumococcal vaccines, including one called a "7-valent protein-conjugated vaccine," which is now recommended for all infants. "This vaccine may be more effective against pneumococcal pneumonia than the vaccine currently used in the elderly, but it needs to be further studied in seniors," she said. As a first step, her team recently began a small study of older people's immune response to the new vaccine.

Jackson added that the emergence of antibiotic-resistant strains of pneumococcal bacteria heightens the importance of finding better ways to prevent pneumococcal infections.

The study was part of the Vaccine Safety Datalink project, which is funded by the Centers for Disease Control and Prevention.

Q & A about pneumonia and the pneumococcol vaccine

What is pneumonia?
Pneumonia is an infection of the lungs that involves the small air sacs and tissues around them.

What causes pneumonia?
Pneumonia can be caused by one of many different microscopic organisms. It usually starts after organisms are inhaled into the lungs, but sometimes the infection is carried to the lungs by the bloodstream or it migrates to the lungs directly from a nearby infection.

In adults, the most common cause of pneumonia is a bacterium called Streptococcus pneumoniae, also called pneumococcus. This bacterium accounts for approximately one third to one half of the estimated 350,000 to 620,000 hospitalizations for pneumonia of all causes each year among Americans aged 65 and older.

In this study, the investigators compared the risk of hospitalized and outpatient pneumonia between people who had received the pneumococcal polysaccharide vaccine and those who did not. The researchers could not directly assess the association of vaccination and risk of pneumococcal pneumonia specifically because for most cases of pneumonia the exact cause is not identified.

Pneumonia can also be caused by viruses such as influenza.

Does the pneumococcal polysaccharide vaccine reduce the risk pneumonia?
No. According to the recent Group Health study, the pneumococcal polysaccharide vaccine does not reduce the overall risk of pneumonia.

However, the pneumococcal polysaccharide vaccine iseffective in preventing bloodstream infection with the pneumoccocus bacterium, which can be associated with pneumonia. Although this bloodstream infection is relatively uncommon, it is the most serious form on pneumococcoal infection and is fatal in about 20 percent of cases.

Should seniors continue to get the pneumococcal polysaccharide vaccine?
Yes. The vaccine is currently recommended for people over age 65 as well as younger people with chronic illnesses, such as heart or lung disease or diabetes, and people with weakened immune systems. New evidence from the Group Health study does not change this recommendation.

In addition, seniors should get annual flu vaccines to protect them against pneumonia and other illness caused by the influenza virus.

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