Pediatric Pneumococcal Vaccine: Possibly Wider Efficacy Than Expected
Not only have US rates of pneumococcal meningitis dropped. The reduction in pediatric hospitalizations for pneumonia has been sustained since the introduction of the pneumococcal conjugate vaccine PCV7 (Prevnar; Wyeth) in 2000, reports the CDC. An update of the center's surveillance data for the years 2005 and 2006 is available in today's issue of the MMWR.
By drawing on data from a nationwide inpatient database,* the CDC found pediatric hospitalization rates (per 1000 children) for all-cause pneumonia and nonpneumonia acute respiratory illness (ARI) as follows:
|
Patient Group |
1997-1999 |
2005 |
2006 |
Rate Ratio |
|
All-cause pneumonia | ||||
|
<2 years |
12.5 |
9.1 |
8.1 |
0.7 |
|
2-4 years |
4.1 |
4.8 |
3.9 |
1.0 |
|
Nonpneumonia ARI | ||||
|
<2 years |
28.1 |
24.6 |
21.9 |
0.8 |
|
2-4 years |
5.8 |
6.5 |
5.6 |
1.0 |
According to the report, the rate reduction for all-cause pneumonia in 2006 represented an estimated 36,300 fewer hospitalizations for children younger than 2 years of age (when compared with the 1997-1999 period). Likewise, the rate reduction for nonpneumonia ARI in 2006 represented an estimated 51,500 fewer hospitalizations in the same age group.
Rate reductions for all-cause pneumonia in children aged 2-4 years were not observed, despite the fact that rates of invasive pneumococcal disease have definitely decreased in this age group since the introduction of PCV7. The authors speculate that organisms other than Streptococcus pneumonia may be more common causes of pneumonia in this age group.
Nevertheless, these data suggest that the benefits of PCV7 extend beyond those of reducing the incidence of invasive disease that is known to be due to S. pneumonia (although the CDC stresses that a causal relationship between vaccination and hospitalizations has not been established).
The concomitant decline in the rates of nonpneumonia ARI among children younger than 2 years of age indicates that the reduction in hospitalizations for all-cause pneumonia is not due to a shift in coding behavior. One explanation for this reduction is that S. pneumoniae may contribute to a wider range of childhood respiratory illnesses than previously thought. Data from trials assessing a 9-valent PCV in Israel and South Africa support this conjecture.
* The Nationwide Inpatient Sample, which contains data on inpatient stays from states that participate in the Healthcare Cost and Utilization Project. Information for roughly 8 million hospitalizations in 2006 was recorded.
Scanning electron micrograph of S. pneumoniae from the CDC/Dr. Richard Facklam.
