Nasopharyngeal colonization: A target for pneumococcal vaccination

Helena Käyhty, Kari Auranen, Hanna Nohynek, Ron Dagan, Helena Mäkelä, Jukka Jokinen, Terhi Kilpi, Marilla Lucero, Veronica Tallo, Shabir Madhi, Peter Adrian, Keith Klugman, David Goldblatt, Anthony Scott, Kate O'Brien, Kim Mulholland, Fiona Russel

Research output: Contribution to journalReview articlepeer-review

Abstract

The pneumococcal conjugate vaccine (PCV), licensed in 2000, is highly efficient in preventing serious disease caused by serotypes in the vaccine and also prevents symptomless colonization of the nasopharynx. Prevention of this first step in the infection cycle has important consequences: it reduces chances of spread of the infection and indirectly protects from disease. Through these indirect effects, the protection afforded by the vaccine extends to the whole population, including those not vaccinated (herd immunity). Already now, after 5 years of wide use of PCV for infant immunization in the USA, more cases are prevented through the indirect effects than by vaccine-induced immunity in those vaccinated. The extended protection increases the cost-effectiveness of PCV and should clearly encourage its use in poorly resourced countries. However, the accumulated experience also shows that the herd immunity, due to PCV, is partly offset by replacement of the vaccine serotypes by other, nonvaccine serotypes. Owing to the general reduced virulence of the latter, this has only had a modest effect on disease, but the possibility of more virulent nonvaccine serotypes arising cannot be ignored and should be the focus of continued surveillance.

Original languageEnglish (US)
Pages (from-to)651-667
Number of pages17
JournalExpert review of vaccines
Volume5
Issue number5
DOIs
StatePublished - Oct 1 2006

Keywords

  • Indirect effects of vaccination
  • Invasive pneumococcal disease
  • Pneumococcal carriage
  • Pneumococcal colonization
  • Pneumococcal conjugate vaccines
  • Pneumococcus

ASJC Scopus subject areas

  • Immunology
  • Molecular Medicine
  • Pharmacology
  • Drug Discovery

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