Abstract
BackgroundPapua New Guinea (PNG) introduced the 13-valent pneumococcal conjugate vaccine (PCV13) in 2014, with administration at 1, 2, and 3 months of age. PCV13 has reduced or eliminated carriage of vaccine types in populations with low pneumococcal carriage prevalence, carriage density and serotype diversity. This study investigated PCV13 impact on serotype-specific pneumococcal carriage prevalence, density, and serotype diversity in PNG infants, who have some of the highest reported rates of pneumococcal carriage and disease in the world. MethodsNasopharyngeal swabs were collected at 1, 4 and 9 months of age from PCV13-vaccinated infants (n = 57) and age-/season-matched, unvaccinated infants (at approximately 1 month, n = 53; 4 months, n = 57; 9 months, n = 52). Serotype-specific pneumococcal carriage density and antimicrobial resistance genes were identified by qPCR and microarray. ResultsPneumococci were present in 89% of swabs, with 60 different serotypes and four non-encapsulated variants detected. Multiple serotype carriage was common (47% of swabs). Vaccine type carriage prevalence was similar between PCV13-vaccinated and unvaccinated infants at 4 and 9 months of age. The prevalence of non-vaccine type carriage was also similar between cohorts, with non-vaccine types present in three-quarters of samples (from both vaccinated and unvaccinated infants) by 4 months of age. The median pneumococcal carriage density was high and similar at each age group (~7.0 log10genome equivalents/mL). PCV13 had no effect on overall pneumococcal carriage density, vaccine type density, non-vaccine type density, or the prevalence of antimicrobial resistance genes. ConclusionPNG infants experience dense and diverse pneumococcal colonisation with concurrent serotypes from 1 month of age. PCV13 had no impact on pneumococcal carriage density, even for vaccine serotypes. The low prevalence of vaccine serotypes, high pneumococcal carriage density and abundance of non-vaccine serotypes likely contribute to the lack of PCV13 impact on carriage in PNG infants. Indirect effects of the infant PCV programs are likely to be limited in PNG. Alternative vaccines with broader coverage should be considered.
Highlights
Streptococcus pneumoniae is a common nasopharyngeal commensal and pathogen, causing a range of major diseases including pneumonia, otitis media, meningitis and sepsis
antimicrobial resistance (AMR) genes were identified in 19% (n = 54) of pneumococcal positive samples: 18.4% from the 13-valent pneumococcal conjugate vaccine (PCV13) cohort versus 16.7% from the unvaccinated cohort at 4 months (p = 0.820); and 11.3% in the PCV13 cohort versus 12.8% in the unvaccinated cohort at 9 months (p = 0.824; Supplementary Table 2)
This study found that PCV13 had no impact on pneumococcal carriage prevalence, carriage density or serotype diversity in Papua New Guinean infants
Summary
Streptococcus pneumoniae (the pneumococcus) is a common nasopharyngeal commensal and pathogen, causing a range of major diseases including pneumonia, otitis media, meningitis and sepsis. The polysaccharide capsule of the pneumococcus is a key virulence factor, with over 100 capsular serotypes identified to date [1] This capsule induces protective antibodies that forms the basis for pneumococcal conjugate vaccines (PCVs), including the currently licensed 10-valent (PCV10) and 13-valent (PCV13) vaccines [2]. PCV13 has reduced or eliminated carriage of vaccine types in populations with low pneumococcal carriage prevalence, carriage density and serotype diversity. This study investigated PCV13 impact on serotype-specific pneumococcal carriage prevalence, density, and serotype diversity in PNG infants, who have some of the highest reported rates of pneumococcal carriage and disease in the world. Vaccine type carriage prevalence was similar between PCV13-vaccinated and unvaccinated infants at 4 and 9 months of age. Conclusion: PNG infants experience dense and diverse pneumococcal colonisation with concurrent
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