From PCV7 to Higher-Valency and Serotype-Agnostic Pneumococcal Vaccines: An Updated Full-Text Bibliometric Evidence Map With Journal-Metric Contextualization

Pneumococcal Vaccines

Abstract

Background: Pneumococcal vaccination now includes PCV10, PCV13, PCV15, PCV20, PPSV23 sequencing, adult strategies, and renewed interest in protein-based or serotype-agnostic vaccines. Conventional bibliometric analyses rarely capture study design, outcomes, or evidence gaps. We therefore mapped full-text articles to characterise the thematic and evidential structure of the accessible literature.

Methods: We conducted a non-probability full-text evidence map of obtainable pneumococcal vaccine articles. Bibliographic characteristics, design, population, vaccine platform, outcomes, findings, limitations, geography, and 13 prespecified themes were extracted and source-verified. Theme presence was coded in a 40 × 13 binary matrix to estimate frequencies and co-occurrence. Descriptive analyses were supplemented by appraisal of evidence type and consistency and a gap analysis based on unresolved questions identified in the articles. Publicly verifiable venue metrics were recorded. Because inclusion depended on full-text availability rather than systematic database searching, findings apply only to the mapped corpus.

Results: Forty articles published during 2015–2026 were included, with peaks in 2024 (n = 9) and 2025 (n = 8), across 25 venues. Designs comprised narrative/scoping reviews (n = 13), modelling/economic evaluations (n = 9), observational surveillance/effectiveness studies (n = 7), systematic reviews with (n = 5) or without meta-analysis (n = 4), one immunogenicity/safety trial, and one other/unclear article. Leading themes were higher-valency PCVs (n = 36), pediatric vaccination (n = 35), effectiveness/impact (n = 32), serotype replacement/carriage and adult vaccination (each n = 22), immunogenicity/safety (n = 15), global health/LMICs (n = 14), economics/policy (n = 13), and high-risk populations (n = 12). PCV13 was mentioned most often (n = 37), followed by PCV7 (n = 30), PCV10 (n = 25), PCV20 (n = 24), PCV15 (n = 23), PPSV23/PPV23 (n = 19), and protein-based/whole-cell approaches (n = 8). Higher-valency PCVs were prominent but supported mainly by modelled or synthesised evidence; no included primary study directly compared PCV15 with PCV20 clinical effectiveness.

Conclusions: The corpus centred on higher-valency conjugate vaccines, life-course/adult vaccination, economics, and residual serotype disease. Key gaps were the absence of primary PCV15-versus-PCV20 comparative effectiveness data, contemporaneous adult carriage evidence, adequate representation of high-burden LMICs, harmonised serotype and outcome definitions in modelling studies, and empirical post-PCV20 replacement data. Protein-based approaches formed a smaller cluster linked mainly to serotype replacement and antimicrobial resistance. These findings describe only the accessible corpus, and venue metrics indicate dissemination context rather than article quality.