Pneumococcal vaccination for prevention of infection and diagnosis of antibody deficiency in the extended conjugated vaccine era.

Purpose of review. Pneumococcal conjugate vaccines (PCV) have transformed pneumococcal disease prevention. Recent expansion to higher-valency formulations (PCV15, PCV20, PCV21) and updated Advisory Committee on Immunization Practices (ACIP) recommendations extending coverage to all healthy PCV-naïve adults ≥50 years in the United States have introduced new complexity in vaccine selection, timing, and dosing. Concurrently, universal childhood conjugate priming complicates the diagnosis of specific antibody deficiency (SAD), as prior PCV immunization alters interpretation of the Pneumococcal polysaccharide vaccines (PPSV23) challenge. This review synthesizes recent evidence on vaccine effectiveness in invasive pneumococcal disease (IPD) prevention, serotype dynamics, and the evolving diagnostic framework for SAD.Recent findings. In October 2024, ACIP expanded pneumococcal vaccination to all PCV-naïve adults ≥50 years. Higher-valency conjugate vaccines continue to reduce invasive pneumococcal disease (IPD), and pipeline data projects that candidate PCV31 vaccine would cover 85-94% of pediatric and adult IPD Accurate diagnosis of SAD remains challenging in the PCV vaccine era stressing the importance of finding a reliable polysaccharide antigen for vaccine challenge., PPSV23 responses must be assessed using non-PCV serotypes in conjugate-primed patients and alternative polysaccharide antigens such as Typhim Vi may offer complementary utility with high specificity but limited sensitivity.Summary. There has been a marked decline in PID in the pneumococcal conjugate vaccine era, yet serotype replacement persists. Vaccine selection now requires individualized decision-making, and SAD diagnosis must be adapted in PCV-primed patients to avoid incorrect interpretation.