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Randomized Controlled Trial
. 2013 Sep 27;8(9):e72198.
doi: 10.1371/journal.pone.0072198. eCollection 2013.

Nasopharyngeal carriage of pneumococci four years after community-wide vaccination with PCV-7 in The Gambia: long-term evaluation of a cluster randomized trial

Anna Roca  1 , Michel M Dione, Abdoulie Bojang, John Townend, Uzochukwu Egere, Ousainou Darboe, Stephen R C Howie, Philip C Hill, Richard A Adegbola, Brian M Greenwood, Martin Antonio
Affiliations
Randomized Controlled Trial

Nasopharyngeal carriage of pneumococci four years after community-wide vaccination with PCV-7 in The Gambia: long-term evaluation of a cluster randomized trial

Anna Roca et al. PLoS One. .

Abstract

Background: A village-randomized trial of a seven-valent pneumococcal-conjugate-vaccine (PCV-7) conducted in rural Gambia showed a decrease of vaccine-type (VT) and a non-significant increase in non-vaccine-type (NVT) nasopharyngeal carriage of pneumococci two years after vaccination. Here, we report findings four years after vaccination.

Methods: PCV-7 was given to all children below 30 months of age enrolled in the trial and to those born during its course in all study villages. Villages were randomized (older children and adults) to receive PCV-7 (wholly vaccinated villages) or serogroup-C-meningococcal-conjugate-vaccine (partly vaccinated villages). Cross-sectional surveys (CSS) to collect nasopharyngeal swabs were conducted before and at various intervals after vaccination. Sixteen of these randomized villages (8 wholly vaccinated and 8 partly vaccinated) participated in a CSS conducted four years after vaccination started.

Results: Four years after vaccination, the prevalence of VT pneumococcal carriage was slightly higher in partly than in wholly vaccinated villages [6.4% versus 3.9% (p = 0.120)] compared to 24.4% in the pre-vaccination CSS (p<0.001). Prevalence of NVT four years after vaccination was similar between study groups [32.7% versus 29.8% (p = 0.392), respectively] compared to 51.1% in the pre-vaccination CSS (p<0.001). Four years after vaccination started, lower prevalence of serotype 6A was detected in wholly vaccinated than in partly vaccinated villages (1.6% versus 3.5%, p = 0.093) whilst the prevalence of serotype 19A was similar between groups (2.9% versus 2.5%, p = 0.779). The most prevalent serotype 19A clone was ST 847. The most prevalent serotype 6A clone before vaccination was ST3324 whilst after vaccination ST913 and ST1737 predominated. Fourteen out of 26 STs detected among the serotype 6A isolates were new while no new 19A serotype ST was found.

Conclusions: The decline in prevalence of VT pneumococci seen shortly after PCV-7 vaccination was sustained four years later with only a small difference between study arms. No significant serotype replacement was detected.

Trial registration: ClinicalTrials.gov ISRCTN51695599.

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Conflict of interest statement

Competing Interests: The authors have the following interests: study vaccines were donated by Wyeth Lederle Vaccines (Pfizer). Adegbola RA is employed by GlaxoSmithKline Vaccines. There are no further patents, products in development or marketed products to declare. This does not alter the authors' adherence to all the PLOS ONE policies on sharing data and materials, as detailed online in the guide for authors.

Figures

Figure 1
Figure 1. Trial profile.
PCV-7: 7-valent pneumococcal conjugate vaccine; CSS-1: Cross-sectional 1; CSS-2: Cross-sectional 2; CSS-3: Cross-sectional 3; CSS-4: Cross-sectional 4.
Figure 2
Figure 2. Prevalence of pneumococcal carriage of any serotype (Any), vaccine serotype (VT), and non-vaccine serotype (NVT) in cross-sectional surveys before and after vaccination with PCV-7 stratified by age group and study arm (solid lines indicate partly vaccinated villages and dashed lines indicate wholly vaccinated villages).
Figure 3
Figure 3. Prevalence of pneumococcal carriage of serotypes 6A (VT group) and 19A (NVT group) in cross-sectional surveys before and after vaccination with PCV-7 stratified by age group and study arm (solid lines indicate partly vaccinated villages and dashed lines indicate wholly vaccinated villages).
See this image and copyright information in PMC

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