Effect on nasopharyngeal pneumococcal carriage of replacing PCV7 with PCV13 in the Expanded Programme of Immunization in the Gambia.


Roca, A; Bojang, A; Bottomley, C; Gladstone, RA; Adetifa, JU; Egere, U; Burr, S; Antonio, M; Bentley, S; Kampmann, B; Pneumo13 Study Group; Oluwalana, C; Idoko, O; Cox, I; Kwambana-Adams, BA; Jarju, S; Foster-Nyarko, E; Greenwood, B; (2015) Effect on nasopharyngeal pneumococcal carriage of replacing PCV7 with PCV13 in the Expanded Programme of Immunization in the Gambia. Vaccine. ISSN 0264-410X DOI: 10.1016/j.vaccine.2015.11.012

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Abstract

In 2011, two years after the introduction of 7-valent Pneumococcal conjugate vaccine (PCV), the Gambian immunization programme replaced PVC7 with PCV13 (13-valent). Our objective was to assess the additional impact of PCV13 on prevalence of pneumococcal nasopharyngeal carriage. We recruited healthy Gambian infants who had received three PCV doses. Nasopharyngeal swabs were collected from infants and their mothers during two cross-sectional surveys (CSS) conducted in infants vaccinated with PCV7 (CSS1) and vaccinated with PCV13 (CSS2). Pneumococci were isolated and serotyped following standardized methods. Whole genome sequencing was performed on non-typable pneumococcus isolated in CSS1 and CSS2. 339 and 350 infants and their mothers were recruited in CSS1 and CSS2, respectively. Overall prevalence of pneumococcal carriage was 85.4% in infants. Among infants, prevalence of vaccine type (VT) carriage was lower in CSS2 [9.4% versus 4.9% (p=0.025) for PCV7-VT; 33.3% versus 18.3% (p<0.001) for PCV13-VT and 23.9% versus 13.7% (p=0.001) for the 6 additional serotypes included in PCV13]. At CSS2, there was a decrease of serotypes 6A (from 15.3% to 5.7%, p<0.001) and 19F (from 5.6% to 1.7%, p=0.007), and an increase of non-typable pneumococci (0.3-6.0%, p<0.001), most of which (82.4%) were from typable serotype backgrounds that had lost the ability to express a capsule. Prevalence of overall and VT carriage in mothers was similar in CSS1 and CSS2. Replacing PCV7 for PCV13 rapidly decreased prevalence of VT carriage among vaccinated Gambian infants. An indirect effect in mothers was not observed yet. Vaccine-driven selection pressure may have been responsible for the increase of non-typable isolates.

Item Type: Article
Faculty and Department: Faculty of Infectious and Tropical Diseases > Dept of Disease Control
Faculty of Epidemiology and Population Health > Dept of Infectious Disease Epidemiology
Faculty of Infectious and Tropical Diseases > Dept of Clinical Research
Research Centre: Vaccine Centre
Tropical Epidemiology Group
PubMed ID: 26592141
Web of Science ID: 366779600004
URI: http://researchonline.lshtm.ac.uk/id/eprint/2373869

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