A vaccine to prevent a dangerous infection that often strikes cystic fibrosis patients is feasible, but needs more development, German researchers report.

Cystic fibrosis is an inherited illness in which thick mucus affects the lungs and digestive system. It affects about 80,000 people worldwide including about 30,000 in the United States.

Over time, some 80 percent of CF patients become infected with the life-threatening Pseudomonas aeruginosa microbe.

Researchers led by Gerd Doering of the University of Tuebingen tested a vaccine against Pseudomonas and report their findings in Tuesday's issue of Proceedings of the National Academy of Sciences.

Over 14 months, 37 patients developed Pseudomonas infection out of 189 treated with the vaccine. By comparison, of 192 receiving a placebo, 59 developed the infection.

"This is the first demonstration that in CF, vaccination against life threatening Pseudomonas aeruginosa lung infection is successful," Doering said. But, he added, "further development of the vaccine formulation is needed."

The company that made the vaccine for his test has since been purchased and the new owner is not interested in developing that product, Doering said.

Gerald B. Pier of Harvard Medical School said the major significance of the report is that the vaccine did have one positive effect, which was to reduce the onset of new infections in CF patients.

"The longer you can delay the onset of lung infection, particularly with Pseudomonas aeruginosa, in CF the better the patients do," he said. "Showing that vaccination can at least partly meet this goal is a very encouraging finding for management of the lung disease that plagues CF patients."

Pier, a cystic fibrosis expert, was not part of Doering's research team, but did review the manuscript before publication.