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Decrease of invasive pneumococcal infections in children among 8 children's hospitals in the United States after the
Sheldon L Kaplan1, Edward O Mason, Ellen R Wald
1Pediatric Infectious Diseases Sections of the Baylor College of Medicine, Houston, Texas, USA. skaplan@bcm.tmc.edu
Insights
The 7-valent pneumococcal conjugate vaccine (PCV7) significantly reduced invasive pneumococcal infections in young children. However, increases in non-vaccine serotypes and evolving penicillin resistance necessitate ongoing surveillance.
Area of Science:
- Pediatric Infectious Diseases
- Vaccinology
- Microbiology
Background:
- Invasive pneumococcal infections pose a significant threat to young children.
- The 7-valent pneumococcal conjugate vaccine (PCV7) was introduced to prevent infections caused by Streptococcus pneumoniae.
Purpose of the Study:
- To evaluate the impact of PCV7 on invasive pneumococcal infections in children.
- To monitor changes in serogroup distribution and antimicrobial susceptibility post-PCV7 introduction.
Main Methods:
- A 9-year prospective surveillance study (1994-2002) was conducted.
- Culture-proven invasive pneumococcal infections in children at 8 US hospitals were analyzed.
Main Results:
- Invasive pneumococcal infections in children under 24 months decreased by 58-66% post-PCV7.
- A significant decline in vaccine-serogroup isolates was observed, with increases in non-vaccine serotypes (15 and 33).
- Penicillin resistance decreased in 2002, but increased slightly among non-vaccine serotypes.
Conclusions:
- PCV7 has dramatically reduced vaccine-serogroup invasive pneumococcal infections in young children.
- Emergence of non-vaccine serotypes and shifts in antibiotic resistance patterns are noted.
- Continued surveillance is crucial to monitor evolving serotype distribution and antimicrobial susceptibility.
Objective:
To monitor clinical and microbiologic features including antimicrobial susceptibility and serogroup distribution of invasive infections caused by Streptococcus pneumoniae among children before and after the introduction of routine administration of the 7-valent pneumococcal conjugate vaccine (PCV7).
Design:
A 9-year (January 1, 1994 through December 31, 2002) prospective surveillance study of all invasive pneumococcal infections in children.
Patients:
Infants and children cared for at 8 children's hospitals in the United States with culture-proven invasive infections caused by S pneumoniae.
Results:
When compared with the mean of the years 1994 to 2000, the annual number of invasive pneumococcal infections for children < or =24 months of age declined 58% in 2001 and 66% in 2002. If only the serogroups in the PCV7 are considered, the number of cases in children < or =24 months old declined 63% and 77% in 2001 and 2002, respectively. The greatest decrease was observed for serogroup-14 isolates. The number of isolates in nonvaccine serogroups increased 28% in 2001 and 66% in 2002 for children < or =24 months old. Nonvaccine serogroup-15 and -33 isolates had the greatest increase in number. The proportion of all isolates nonsusceptible to penicillin increased yearly from 1994 to 2000, reached a plateau in 2001 at 45%, and declined to 33% in 2002. Decrease in nonsusceptibility to penicillin occurred entirely in the isolates with penicillin minimum inhibitory concentration > or =2 microg/mL. Nonsusceptibility to penicillin increased slightly among nonvaccine-serotype isolates. Most infections after at least 2 doses of PCV7 were caused by nonvaccine-serotype isolates.
Conclusions:
Since the introduction of the PCV7, the number of invasive pneumococcal infections caused by vaccine-serogroup isolates among 8 US children's hospitals has decreased >75% among children < or =24 months old. In addition, penicillin resistance decreased in 2002 for the first time since our surveillance began in 1993-1994. However, we have noted that replacement may be developing with serogroups 15 and 33. Furthermore, penicillin resistance seems to be increasing among nonvaccine serogroups. Surveillance must be continued to detect the emergence of changes in the distribution of serotypes as well as antibiotic susceptibility.
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