Pneumococcal Strains Not Covered by Vaccine on the Rise

Vaccine is still effective, but may need to include new strains, study finds.

By Serena Gordon
HealthDay Reporter
Tuesday, April 24, 2007; 12:00 AM

Copyright © 2007 ScoutNews, LLC. All rights reserved.

TUESDAY, April 24 (HealthDay News) -- While the pneumococcal vaccine for children is highly effective, strains of the bacteria not covered by the vaccine are emerging as potential threats in certain populations.

A new U.S. government investigation has found that in Alaskan Native children who are already protected against seven strains of pneumococcal disease due to vaccination, the rate of serious infection by other strains is increasing by as much as 140 percent.

"The vaccine has been very effective and has done exactly what we hoped it would do. It's decreased the incidence of invasive pneumococcal disease (covered by the vaccine strains) by 95 percent in Alaskan Native children," said the study's lead author, Dr. Rosalyn Singelton, a visiting researcher for the U.S. Centers for Disease Control and Prevention in Anchorage, Alaska. "But, we've recently seen a significant increase in emerging non-vaccine serotypes."

The bacterium Streptococcus pneumoniae causes a variety of pneumococcal diseases, according to the CDC. Some are relatively mild, such as ear infections, while others are potentially life-threatening, such as pneumonia, meningitis and blood infections.

In 2000, the PCV7 pneumococcal conjugate vaccine first became available for infants and children. The vaccine includes the seven strains or serotypes of the bacteria that commonly cause pneumococcal disease in the United States.

Alaskan Natives have traditionally had higher rates of pneumococcal disease, according to the study. Before the introduction of the PCV7 vaccine, Alaskan Native children had three times the rate of invasive pneumococcal disease compared to the overall U.S. population. Possible reasons for this, according to Singleton, were overcrowding in small households, spending large amounts of time indoors and a lack of running water in many communities.

The new study, published in the April 25 issue of the Journal of the American Medical Association, included surveillance data from the beginning of 1995 through 2006.