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Serotype replacement in perspective

Ron Dagan1

  • 1Pediatric Infectious Disease Unit, Soroka University Medical Center and the Faculty of Health Sciences, Ben-Gurion University of the Negev, P.O. Box 151, Beer-Sheva 84101, Israel. rdagan@bgu.ac.il

Vaccine
|June 24, 2009
PubMed

Insights

The seven-valent pneumococcal conjugate vaccine (PCV7) has led to increased invasive pneumococcal disease (IPD) from non-vaccine serotypes, particularly 19A, which shows rising antibiotic resistance. Understanding serotype carriage changes is crucial for managing this replacement disease.

Area of Science:

  • Microbiology
  • Epidemiology
  • Vaccinology

Background:

  • The introduction of the seven-valent pneumococcal conjugate vaccine (PCV7) has altered the epidemiology of invasive pneumococcal disease (IPD).
  • An observed increase in IPD caused by non-vaccine serotypes (NVTs), known as serotype replacement, is noted, especially in vulnerable populations.
  • The precise relationship between changes in pneumococcal serotype carriage and the incidence of replacement disease, particularly in young children, remains unclear.

Purpose of the Study:

  • To investigate the impact of PCV7 on pneumococcal serotype distribution and carriage dynamics.
  • To understand the emergence of non-vaccine serotypes (NVTs) causing invasive pneumococcal disease (IPD) post-PCV7 introduction.
  • To assess the antibiotic resistance patterns of predominant NVTs, focusing on serotype 19A.

Main Methods:

  • Epidemiological surveillance of invasive pneumococcal disease (IPD) serotypes before and after PCV7 introduction.
  • Analysis of pneumococcal carriage data in relevant populations, including children under 5 years.
  • Antimicrobial susceptibility testing for isolated pneumococcal strains, particularly non-vaccine serotypes (NVTs).

Main Results:

  • An increase in invasive pneumococcal disease (IPD) incidence due to non-vaccine serotypes (NVTs) has been documented following PCV7 implementation.
  • Serotypes 15, 19A, and 33F are identified as predominant NVTs contributing to replacement disease.
  • A concerning trend of increasing antibiotic resistance, especially in serotype 19A, is observed in both vaccinated and unvaccinated individuals.

Conclusions:

  • The seven-valent pneumococcal conjugate vaccine (PCV7) has driven serotype replacement, leading to increased invasive pneumococcal disease (IPD) from non-vaccine serotypes (NVTs).
  • Serotype 19A is a significant concern due to its increasing prevalence and antibiotic resistance, posing a threat to public health.
  • Further research into pneumococcal carriage dynamics is essential for effective disease prevention and control strategies against emerging NVT strains.

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