This article is more than 5 years old. Information may no longer be current.
PCV7 efficacy continues to reduce invasive pneumococcal disease in U.S.
Click Here to Manage Email Alerts
The incidence of invasive pneumococcal disease caused by 7-valent pneumococcal conjugate vaccine serotypes decreased by 94% between 1998 and 2007, according to results of a recent study.
Researchers analyzed laboratory-confirmed invasive pneumococcal disease cases from eight population-based surveillance sites in the United States between 1998 and 2007. Comparisons were made between 1998-1999, which was prior to the use of the 7-valent pneumococcal conjugate vaccine (PCV7) and 2007.
Areas of comparison included overall, age group-specific, syndrome-specific and serotype group-specific invasive pneumococcal disease incidence.
Incidence of overall pneumococcal disease declined by 45%, from 24.4 to 13.5 cases per 100,000 population, during the study period (P,.01 for all age groups). The decline was 94%, from 15.5 to 1.0 cases per 100,000 population, for PCV7-type disease (P,.01 for all age groups).
An increase from 0.8 to 2.7 cases per 100,000 population was observed for serotype 19A, and an increase from 6.1 to 7.9 cases per 100,000 population was observed for other non-PCV7 types (P,.01 for all age groups).
Increases were observed in all age groups for meningitis and invasive pneumonia caused by non-PCV7 types (P,.05). The rates of primary bacteremia caused by these serotypes were unchanged.
PCV7 serotypes accounted for 2% of invasive pneumococcal disease during 2006 and 2007. The six other serotypes included in an investigational 13-valent conjugate vaccine accounted for 63% of invasive pneumococcal disease cases among children younger than five.
Pilishvili T et al. J Infect Dis. 2009;201:32-41.
A key observation of this paper is that PCV7-type IPD incidence continued to decline through 2007. However, reductions in overall IPD during 2002–2007 were offset by increases in IPD serotypes not included in PCV7, predominantly serotype 19A. Rates of IPD caused by serotype 19A increased for all ages, making this serotype now the most common among all age groups. In spite of this, these results should be kept in perspective. Absolute increases in rates of non–PCV7-type IPD remain modest in comparison with the reductions in PCV7-type IPD observed since 2000.
A second key finding was the observed significant increases in incidence of meningitis and invasive pneumonia caused by non-vaccine serotypes, suggesting that 19A and other circulating non-PCV7 serotypes have a predilection to cause a different spectrum of pneumococcal diseases. Furthermore, the incidence of hospitalization or death increased among patients with IPD who were hospitalized in all age groups.
The overall trends of IPD during 2002–2007 reached an equilibrium between reductions in PCV7-type IPD and increases in non-PCV7 serotype IPD. Especially disturbing is an increased propensity to meningitis and death among current cases, likely due in part to increasing antibiotic resistance among non-PCV7 strains, especially serotype 19A. Clinicians must be vigilant in considering serotype 19A “superbugs”. Fortunately, a new higher-valency conjugate vaccine should be licensed in 2010 that contains serotype 19A and several other important emerging pneumococcal serotypes. Assuming their effectiveness is similar to that of PCV7, the new PCV13 should be able to prevent pneumococcal disease caused by a greater variety of serotypes. Use of conjugate vaccines among adults, especially those with underlying illnesses, may also play an important role. The longer term solution may lie in pneumococcal vaccines that contain a mix of common proteins expressed by all pneumococci, thereby obviating the challenge of serotype replacement among pneumococcal strains. Such vaccines are now under development.
- Michael Pichichero, MD
Clinical Professor, Department of Pediatrics, Rochester University of Medicine