Study Evaluating Streptococcus Pneumoniae Nasopharyngeal Carriage Rate in Children Receiving Prevnar®
Condition: Pneumococcal Infections
MeSH terms: Pneumonia; Pneumonia, Pneumococcal; Pneumococcal Infections
Study type: Observational

Summary: 
      Primary Objective:

      To evaluate the impact of PCV7 vaccination on NP carriage rate of vaccine serotypes and
      serotype distribution

      Secondary Objective:

      To evaluate the impact of PCV7 vaccination on NP carriage of antibiotic resistant pneumococci
      and serotype distribution.
    

Detailed description: 
      Under the Social Welfare Vaccination Program, the Taipei City Government will vaccinate
      approximately 5,000 children residing in the city of Taipei between 2 and 5 years of age
      during the months of November 2006 to April 2007 with one dose of PCV7.

      To gather baseline data on serotype distribution and antibiotic resistance of nasopharyngeal
      (NP) carriage isolates in this population and measure vaccine impact on NP carriage, the
      Taipei city government requires the evaluation of the vaccination program through the
      detection of Streptococcus pneumoniae NP carriage rate pre and post vaccination in a
      convenience sample of approximately 1000 children. This number complies with the Taipei city
      government request for the inclusion of 250 children.

      Streptococcus pneumoniae is a major cause of bacterial otitis media, pneumonia, sepsis,
      bacteraemia, and meningitis among infants worldwide.

      The main reservoir of pneumococci is the human nasopharynx. The mean age of first acquisition
      is 6 months and carriage rates peak in the preschool age group. The organisms have pilli on
      their surface to assist in adhering to nasopharyngeal mucosal receptors. Streptococcus
      pneumoniae is part of the normal flora in colonized individuals, but the organism has the
      ability to cause disease by invading neighboring tissues, and potentially spreading into the
      bloodstream and other sites, causing invasive pneumococcal disease, such as bacteremia,
      sepsis and meningitis. The rate of NP carriage for Streptococcus pneumoniae in Taiwan
      (1998-99) was estimated to be 19.9 % overall for children 1-14 years and 27.1 % for those 2-5
      years. A more recent study by Lauderdale et al. found a carriage rate of 41 % in children
      attending a kindergarten program in Taiwan where a 5 year old was diagnosed with
      streptococcus meningitis.

      Prevnar® has shown a high degree of efficacy in the prevention of invasive pneumococcal
      disease in children. In addition, PCV7 has been shown to decrease NP carriage of serotypes
      included in the vaccine (VST). Since NP carriage is a prerequisite for transmission of
      Streptococcus pneumoniae, decrease in NP carriage of VSTs in children has resulted in
      decreased transmission to their contacts and an indirect effect (herd effect) on invasive
      pneumococcal disease. Since the majority of antibiotic resistant strains are VST, PCV7
      immunization has decreased antibiotic resistance in invasive pneumococcal disease for both
      those immunized and their contacts. However, after PCV7 vaccination overall pneumococcal NP
      carriage rates do not change, since Streptococcus pneumoniae serotypes not included in the
      vaccine (NVST) replace the VSTs. Although in the nasopharynx there is an almost complete
      replacement by NVST, these serotypes may have less ability to cause invasive disease, since
      disease with NVST has been observed but to a much lower magnitude than disease prior to PCV7
      vaccination.

      Thus, the expected outcome of a successful PCV7 vaccination program on NP carriage is a
      decrease in carriage of VST with an increase in NVST and thus, a stable overall Streptococcus
      pneumoniae carriage rate.
    

Intervention name(s): Pneumococcal Conjugated Vaccine (Prevnar®)
Intervention type(s): Biological
Intervention MeSH terms: Heptavalent Pneumococcal Conjugate Vaccine
Time perspective: Prospective
Keywords: Streptococcus pneumoniae nasopharyngeal carriage