Kids’ vaccine guards adults too, for now

From Boston, at a meeting of the Infectious Diseases Society of America

Following the national introduction in 2000 of a vaccine for children against seven common strains of pneumococcus, serious infections caused by the bacteria decreased in children. The resulting dip in the microbe’s overall prevalence in kids led to fewer infections in adults. A concern, however, is that rare strains of pneumococcus may arise to replace those cut down by the vaccine.

Infection with HIV, the AIDS virus, puts people at particular risk from pneumococcus, so researchers in several states collected 6 years’ worth of data on severe pneumococcal infections among adults with HIV. The researchers also analyzed bacteria taken from those people to determine which pneumococcus strain was responsible.

Compared with the years before 2000, pneumococcal infections in late 2002 and early 2003 were 21 percent less frequent among adults with HIV, says Brendan Flannery of the Centers for Disease Control and Prevention in Atlanta. That improvement mirrors the effect seen among healthy adults, and it reflects a steep decline in infections caused by the seven strains the vaccine blocks.

However, the data also showed that infections caused by other strains of pneumococcus have become more common among people with HIV, Flannery says. That group may therefore serve as a “sentinel population” in which researchers can anticipate rises in vaccine-resistant strains of pneumococcus.