Researchers have found that PCV7, a pneumococcal conjugate vaccine introduced in the United States 10 years ago, appears to reduce pneumonia and serious associated complications, such as blood infections, in children less than a year old—the vaccine’s target range. However, pneumonia and associated complications, including a lung infection called empyema, increased in older children. The findings of The Children’s Hospital of Philadelphia study were published in the journal Pediatrics.

The vaccine is administered to infants to prevent infection with the Streptococcus pneumoniae bacteria, the leading bacterial cause of pneumonia. S.pneumoniae, or pneumococcus, also causes ear infections, sinusitis, blood infections, and meningitis. PCV7 protects against seven of the most common of the 90 strains of pneumococcal bacteria. A recently licensed pneumococcal vaccine now protects against the 13 most common strains.

The study looked at 619,102 patients younger than 18 years old who were hospitalized for “community-acquired pneumonia” in the years 1997, 2000, 2003, or 2006 and recorded in the national Kids’ Inpatient Database.

The rate of hospitalizations for community-acquired pneumonia in the first year of life declined by 22% from 1997 to 2006, according to the study. Conversely, the rate of hospitalizations for pneumonia in children 6 to 12 increased 22%, and for children over 13 the rate increased by more than 40%. Lung complications related to pneumonia, such as empyema, were highest in children ages 1 to 5 years.

“This is the first national study to comprehensively examine rates of pneumonia-related complications before and after the introduction of the PCV7 vaccine,” said Grace E. Lee, MD, a lead researcher in the study and pediatric infectious diseases fellow at Children’s Hospital. “Rates of systemic complications such as sepsis and respiratory failure decreased by 9% overall and approximately 35% for infants less than one year of age. The overall 9% decrease in systemic complication rates for the entire population in the study was largely attributable to the decrease in rates for infants and might be explained in part by the fact that infants have been the primary recipient of the vaccine.”

“In contrast, rates of hospitalization for lung complications such as empyema increased by more than 70% for children between one and 18 years of age,” added Lee. The reasons for such increases are not yet known.

The vaccine may also disproportionately benefit black children, shown in past studies to have a higher frequency of pneumococcal infections, including pneumonia. While rates of pneumonia were higher for black children compared to white children in all years of this study, the difference narrowed from a ratio of 1.98 in 1997 to a ratio of 1.59 in 2006.

Source: The Children’s Hospital of Philadelphia