October 27, 2003

Vaccine proves effective against pneumonia

By Holly Korschun


In a clinical trial conducted on nearly 40,000 young children in Soweto, South Africa, a new vaccine aimed at nine strains of pneumonia reduced incidence of the disease in fully vaccinated children by 25 percent.

In addition, the vaccine reduced the incidence of invasive pneumococcal disease (pneumococcal bacteria in the bloodstream) by more than 83 percent in non-HIV-infected children and by more than 65 percent in HIV-infected children. The vaccine also significantly reduced the incidence of invasive pneumococcal disease caused by antibiotic-resistant strains by between 56 and 67 percent, depending on the type of resistance.

The study took place between 1998 and 2000, with follow-up through 2001. The results were published in the Oct. 2 issue of The New England Journal of Medicine.

Participating institutions included Emory, the University of the Witwatersrand in South Africa, Johns Hopkins University and Wyeth Pharmaceuticals, under the auspices of the World Health Organization (WHO) and the Medical Research Council of South Africa. Keith Klugman, professor of international health in the Rollins School of Public Health and professor of medicine in the School of Medicine, was principal investigator of the study.

The clinical trial randomized two groups of infants to receive either three doses of the conjugate vaccine or placebo. In addition, all children received Haemophilus influenzae type b (Hib) conjugate vaccine. The scientists tracked the conjugate vaccine’s effectiveness over a four-year period through active surveillance of children with pneumococcal disease at the large academic hospital serving Soweto.

Antibiotic-resistant strains of pneumococci are common in the community, and HIV infection is the leading risk factor for invasive pneumococcal disease. The overall mortality rate in the clinical trial was reduced by 5 percent among all children and by 6 percent among those with HIV.

"With this reduction in the incidence of pneumonia in the developing world, we could potentially save more than 500,000 lives each year," Klugman said. "In addition, no vaccine previously has been documented to prevent pneumococcal disease in HIV-infected children, and our study showed a 50 percent reduction in that group.

"In an era in which there is little to offer children with HIV, we can reduce invasive disease by providing this vaccine to all children," he continued. "Our study provides evidence to support the use of this vaccine to prevent invasive pneumococcal disease, reduce antibiotic resistance and diminish the incidence of pneumonia in children."

According to the WHO, pneumonia is the leading cause of death in children worldwide and is responsible for approximately 4 million deaths a year. Most of these deaths occur in developing countries. Strepto-coccus pneumoniae, the primary bacterial pathogen leading to pneumonia, has become increasingly resistant to antibiotics.

The new vaccine holds promise for all U.S. children to prevent invasive pneumococcal disease and bacterial meningitis, and it can be administered in infancy. It targets seven strains of pneumococcal disease, while the vaccine used in the South African trial targets two additional strains that are prevalent in developing countries. The conjugate vaccine is currently under development for both developed and developing countries but has not yet been licensed for use.