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Pneumococcal serotype 3 otitis media, limited effect of polysaccharide conjugate immunisation and strain

Jan Poolman1, Pavla Kriz, Christiane Feron

  • 1GlaxoSmithKline Biologicals, Rixensart, Belgium. jan.poolman@gskbio.com

Vaccine
|May 19, 2009
PubMed
Abstract

Insights

Pneumococcal conjugate vaccines show limited efficacy against serotype 3 acute otitis media (AOM). This may be due to impaired immune memory or abundant capsular polysaccharide expression hindering antibody defense.

Area of Science:

  • Immunology
  • Vaccinology
  • Microbiology

Background:

  • The POET study revealed no protection against serotype 3 acute otitis media (AOM) following vaccination with a multi-valent pneumococcal conjugate vaccine.
  • This contrasts with the vaccine's efficacy against other serotypes.

Purpose of the Study:

  • To investigate the reasons for the lack of efficacy against serotype 3 AOM.
  • To evaluate the pheno- and genotypic characteristics of serotype 3 strains in relation to vaccine response.

Main Methods:

  • Review of AOM efficacy and immunogenicity data from the POET study.
  • Phenotypic and genotypic characterization of serotype 3 Streptococcus pneumoniae strains, including isolates from the efficacy study.

Main Results:

  • Lack of efficacy against serotype 3 may be linked to diminished protection after booster doses.
  • Atypical immunogenicity for serotype 3 was observed, yet the ability to respond to plain polysaccharide was not impaired.
  • Most serotype 3 strains possessed abundant polysaccharide capsules; lower mRNA transcript levels were noted in a less encapsulated strain.

Conclusions:

  • Impaired immune memory induction could explain the lack of clinical efficacy against serotype 3 AOM.
  • Atypical abundant capsular polysaccharide expression might reduce susceptibility to antibody-mediated defense.
  • The clinical value of vaccines containing pneumococcal serotype 3 components for otitis media requires further investigation.

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