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

Abstract Introduction In 2011, two years after the introduction of 7-valent Pneumococcal conjugate vaccine (PCV7), 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...

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Bibliographic Details
Published in:	Vaccine 2015-12, Vol.33 (51), p.7144-7151
Main Authors:	Roca, Anna, Bojang, Abdoulie, Bottomley, Christian, Gladstone, Rebecca A, Adetifa, Jane U, Egere, Uzochukwu, Burr, Sarah, Antonio, Martin, Bentley, Stephen, Kampmann, Beate
Format:	Article
Language:	eng
Subjects:	Adult Africa Age Allergy and Immunology Carrier State - epidemiology Carrier State - microbiology Carrier State - prevention & control Cross-Sectional Studies Developing countries Epidemiology Expanded Programme of Immunization Female Gambia - epidemiology Health facilities Humans Infant Laboratories LDCs Male Medical research Nasopharynx - microbiology Non-typable PCV13 PCV7 Pneumococcal Infections - epidemiology Pneumococcal Infections - microbiology Pneumococcal Infections - prevention & control Pneumococcal Vaccines - administration & dosage Pneumococcal Vaccines - immunology Pneumonia Prevalence Sequence Analysis, DNA Serogroup Serotyping Streptococcus pneumoniae Streptococcus pneumoniae - classification Streptococcus pneumoniae - genetics Streptococcus pneumoniae - isolation & purification Studies Vaccine-type Vaccines Young Adult
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Summary:	Abstract Introduction In 2011, two years after the introduction of 7-valent Pneumococcal conjugate vaccine (PCV7), 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. Methods 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. Results 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. Conclusions 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.
ISSN:	0264-410X 1873-2518