Effect of the 7-valent pneumococcal conjugate vaccine on nasopharyngeal colonization by Streptococcus pneumoniae in the first 2 years of life

Clin Infect Dis. 2004 Oct 1;39(7):930-8. doi: 10.1086/423379. Epub 2004 Sep 13.


Background: Studies suggest that the 7-valent pneumococcal conjugate vaccine (PCV7) reduces carriage of vaccine-type (VT) Streptococcus pneumoniae (SP). We studied the effect of PCV7 on carriage of VT- and non-VT (NVT) SP, by studying the effect of PCV7 on nasopharyngeal (NP) colonization by VT and NVT SP during early childhood.

Methods: At 2 months of age, 278 infants were enrolled in this study. To determine carriage of SP, NP samples were obtained before each PCV7 dose, at 9 months of age, and 2-3 months after the booster dose of vaccine.

Results: The carriage of SP increased slightly, from 12% (95% confidence interval [CI], 8%-16%) of subjects at 2 months of age to 18% (95% CI, 13%-23%) at 4 months of age (P<.05). Carriage of SP remained in 24%-30% of subjects during subsequent months. Between the 12- and 18-month visits, the carriage rate of VT SP decreased significantly, from 18% (95% CI, 13%-23%) to 9% (95% CI, 5%-13%) of subjects (P=.001). The trend of a decrease in carriage of penicillin-nonsusceptible SP, from 16% of subjects (95% CI, 11%-21%) at the 12-15-month visit to 9% (95% CI, 5%-13%) at the 15-18-month visit, was found after the booster dose of vaccine.

Conclusion: The reduction of VT-SP colonization and replacement by NVT SP after the booster dose of vaccine suggests the possibility that widespread vaccination will result in replacement of pneumococci mainly by antibiotic-susceptible NVT SP.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carrier State / microbiology*
  • Cohort Studies
  • Drug Administration Schedule
  • Female
  • Humans
  • Infant
  • Male
  • Nasopharynx / microbiology*
  • Pneumococcal Vaccines / immunology*
  • Streptococcus pneumoniae / isolation & purification*
  • Vaccines, Conjugate / immunology


  • Pneumococcal Vaccines
  • Vaccines, Conjugate