While a new vaccine has all but eradicated common causes of pneumonia, meningitis and ear infections in children, new strains of bacteria not covered by the vaccine have emerged, U.S. researchers said on Tuesday. Since the introduction of Wyeth's wildly successful vaccine Prevnar in 2000, doctors have been waiting and watching for the arrival of replacement bacteria that could undo its progress.

Now they may have found it. Researchers from the U.S. Centers for Disease Control and Prevention have noted an increase in the rates of bacterial infections not covered by the current pneumococcal vaccine among native children in Alaska. "People are on top of it. It is not unexpected, but it is important," Dr. Katherine Poehling of Brenner Children's Hospital at Wake Forest University in Winston-Salem, North Carolina, said in a telephone interview.

The vaccine, also called heptavalent pneumococcal conjugate vaccine or PCV7, is marketed as Prevnar in the United States and Canada and as Prevenar elsewhere in the world. Given initially at 2, 4 and 6 months of age, it protects children from bacteria that often cause ear infections and drug-resistant pneumonia.
"Because of the surveillance, we are seeing it and we can act in a timely manner and maintain the benefits that we've seen," said Poehling, who wrote a commentary on the study, published in the Journal of the American Medical Association.

The CDC's Dr. Rosalyn Singleton and colleagues studied pneumococcal infections such as pneumonia, meningitis, or blood infections known as bacteremia that occurred from 1995 through 2006. They found that in the three years after introduction of Prevnar, from 2001 through 2003, these diseases fell by 67 percent among native Alaskan children younger than age 2 and 61 percent in non-native children in the same age group.

Between 2001-2003 and 2004-2006, these infection rates remained stable in non-native Alaskan children younger than 2, but jumped 82 percent among Alaska Native children, who are more prone to the infections. Since 2004, diseases caused by strains of bacteria not covered by the vaccine have risen by 140 percent compared with the pre-vaccine period. During the same period, diseases caused by the vaccine-covered strains fell by 96 percent.

"The big news is the vaccine is highly successful. It has prevented a tremendous amount of disease, and it is still preventing a lot of disease in these children," Poehling said. She said a new vaccine by Wyeth is in late-stage clinical trials that could help protect against these new strains. The current vaccine, one of Wyeth's biggest-selling products with annual sales of more than $2 billion, targets seven strains of pneumococcal bacterial. The new vaccine would target 13 strains of the bacterial. Wyeth has said it plans to seek regulatory approvals for the new vaccine in early 2009. GlaxoSmithKline is working on a rival to Prevnar.

Copyright 2007 Reuters Limited