Five winters of pneumococcal serotype replacement in UK carriage following PCV introduction

• DOI: 10.1016/j.vaccine.2015.03.012
• Publication Date: 2015-03-14T07:29:37Z
• Authors: Rebecca A. Gladstone; Johanna M. Jefferies; Anna S. Tocheva; Kate R. Beard; David Garley; Wei Wei Chong; Stephen D. Bentley; Saul N. Faust; Stuart C. Clarke
• Keywords: Male; 0301 basic medicine; Heptavalent Pneumococcal Conjugate Vaccine; Time Factors; Genotype; 610; Serogroup; Article; Pneumococcal Infections; 618; Pneumococcal Vaccines; 03 medical and health sciences; Next generation sequencing; Immunology and Microbiology(all); Nasopharynx; Humans; Serotyping; Whole genome; Public Health, Environmental and Occupational Health; High-Throughput Nucleotide Sequencing; Infant; Pneumococcal vaccines; Sequence Analysis, DNA; veterinary(all); United Kingdom; 3. Good health; Serotype replacement; Infectious Diseases; Streptococcus pneumoniae; Child, Preschool; Carrier State; Molecular Medicine; Female; Seasons; Genome, Bacterial

The seven-valent pneumococcal conjugate vaccine (PCV7) was added to the UK national immunisation programme in September 2006. PCV13 replaced PCV7 in April 2010. As carriage precedes disease cases this study collected carried pneumococci from children each winter from 2006/7 to 2010/11 over PCV introduction. Conventional microbiology and whole genome sequencing were utilised to characterise pneumococcal strains. Overall prevalence of pneumococcal carriage remained stable. Vaccine serotypes (VT) decreased (p<0.0001) with concomitant increases in non-vaccine serotypes (NVT). In winter 2010/11 only one isolate of PCV7 VT was observed (6B). PCV13 unique VTs decreased between winters immediately preceding and following PCV13 introduction (p=0.04). Significant decreases for VTs 6B, 19F, 23F (PCV7) and 6A (PCV13) and increases for NVT 21, 23B, 33F and 35F were detected. The serotype replacement was accompanied by parallel changes in genotype prevalence for associated sequence types with clonal expansion contributing to replacement. By winter 2010/11, serotype coverage of PCV7 and PCV13 was 1% and 11% respectively. VT replacement was observed for PCV7 and PCV13 serotypes. Conjugate vaccine design and use requires continuous monitoring and revision.