THURSDAY, Jan. 14, 2010 (HealthDay News) -- Since the PCV7 early childhood vaccine for bacterial pneumonia was introduced in the United States in 2000, the number of children hospitalized for pneumonia because of pneumococcus has decreased by 50 percent and bacterial pneumonias have decreased overall, new research shows.
But the scientists also found a 70 percent increase in the rate of a pneumonia complication called empyema, a serious and sometimes life-threatening infection in a cavity between the lung and chest wall.
This dramatic rise in the incidence of empyema may partly be because the PCV7 eliminates certain types of pneumococcus, which provides an opportunity for more virulent and antibiotic-resistant types of bacteria to take its place, said the researchers at the University of California, Davis, Children's Hospital.
The increase "may be occurring because the vaccine does not affect the types of microorganisms causing empyemas," study author Su-Ting T. Li, an assistant professor in the pediatrics department, said in a news release. "The vaccine may be getting rid of the pneumococcal bacteria that cause most pneumonia and other types of invasive pneumococcal disease. But the bacteria that are left over that [the vaccine] doesn't protect against that are more likely to cause empyema may increase because they don't have to compete against the other pneumococcal bacteria anymore."
For their study, Li and colleagues analyzed data from the national Kids' Inpatient Database for the years 1997, 2000, 2003 and 2006. From 1997 to 2006, the empyema-associated hospitalization rate for children aged 18 and younger increased 70 percent, from 2.2 per 100,000 to 3.7 per 100,000. The rate of complicated pneumonia -- which includes empyema, pleural effusion or bacterial pneumonia requiring a chest tube or decortication -- increased 45 percent between 1997 and 2006, when the rate was 5.5 per 100,000.
From 1997 to 2006, the rate of bacterial pneumonia hospitalizations decreased 13 percent, to 244.3 per 100,000, and the rate of invasive pneumococcal disease -- pneumonia, sepsis or meningitis caused by Streptococcus pneumoniae -- decreased 50 percent to 6.3 per 100,000.
The mean age of children hospitalized with empyema decreased from slightly more than seven in 1997 to just above six in 2006. Among children younger than 5, the rate of empyema increased 100 percent, from 3.8 per 100,000 in 1997 to 7.6 per 100,000 in 2006.
The study appears in the January issue of Pediatrics.
The Nemours Foundation has more about children and pneumonia.