PCV13-vaccinated children still carrying PCV13 additional serotypes show similar carriage density to a control group of PCV7-vaccinated children

Ron Dagan, Christine Juergens, James Trammel, Scott Patterson, David Greenberg, Noga Givon-Lavi, Nurith Porat, William C. Gruber, Daniel A. Scott

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


Background In addition to reducing vaccine-type nasopharyngeal carriage rates, pneumococcal conjugate vaccines (PCVs) may decrease carriage density in vaccinated individuals still carrying vaccine serotypes. However, reduction of carriage density has not been systematically studied. This study compared the effect of PCV13 versus PCV7 on carriage density of the serotypes in PCV13 that are not included in PCV7. Methods This randomized, double-blind study was conducted in southern Israel and included Jewish and Bedouin subjects. Per protocol, 881 and 873 infants received PCV13 and PCV7, respectively, at ages 2, 4, 6, and 12 months. Nasopharyngeal cultures at ages 7, 12, 13, 18, and 24 months were plated using the 4-quadrant semiquantitative method and graded 0 (negative) to 4 (growth in all plate quadrants). In this post hoc analysis, the least squares means of cumulative colonization densities per serotype and serotype combination of the total population and each ethnic subpopulation in each vaccine group were calculated, and differences between vaccine groups derived from a linear model. Results PCV13-vaccinated children still carrying the 6 additional PCV13 serotypes unique to PCV13 showed no significant differences in carriage density compared with the PCV7-vaccinated control group. No differences in carriage density were shown between Jewish and Bedouin subpopulations despite higher carriage rates among Bedouin subjects. Conclusions Although PCV13 vaccination reduces vaccine-type carriage compared with PCV7 vaccination by reducing nasopharyngeal acquisition of the additional PCV13 serotypes as previously reported, the current study lacks evidence of a decrease in carriage density of these serotypes when acquired in vaccinated children. Despite the lack of effect on carriage density observed, surveillance data suggest a dramatic decrease in disease rates after PCV implementation. Thus, the current analysis suggests that PCV's impact on carriage density has minimal or no impact on vaccine success. (www.ClinicalTrials.gov:

Original languageEnglish
Pages (from-to)945-950
Number of pages6
Issue number6
StatePublished - 7 Feb 2017
Externally publishedYes


  • Density
  • Indirect protection
  • Nasopharyngeal carriage
  • Pneumococcal conjugate vaccine
  • Streptococcus pneumoniae


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