Pneumococcal conjugate vaccines in older adults and immunocompromised individuals

Abstract

Introduction: Pneumococcal disease leads to high morbidity and mortality, particularly in older adults and immunocompromised individuals. Many pneumococcal conjugated vaccines (PCVs) have become available. However, the immunogenicity, efficacy, and effectiveness data of these vaccines in older adults and immunocompromised individuals are limited.

Areas covered: This review aims to critically examine the immune responses, immune correlations, efficacy, real-world effectiveness, and cost-effectiveness of pneumococcal conjugated vaccines (PCVs) in older adults and immunocompromised individuals.

Expert opinion: A single dose of 20-valent or 21-valent PCV is recommended for older adults and immunocompromised individuals. Immune correlates of protection vary by serotype and race. An IgG level of 0.35 µg/mL is associated with protection, though this threshold is serotype-dependent. Opsonophagocytic assays, with a threshold of 1:8, remain the most reliable functional correlate of protection against invasive pneumococcal disease. Standardized immunological assays are essential for evaluating immune responses. High-valent PCVs have shown noninferior immunogenicity compared to PCV13, though geometric mean fold rises (GMFRs) for shared serotypes are slightly lower. Real-world effectiveness data are still needed, particularly in regions with differing serotype prevalence. Serotype surveillance is crucial when introducing PCV programs. Due to the high cost of higher-valent PCVs, many countries continue using PCV13 or PCV15 followed by PPSV23 for high-risk groups.

Keywords: Pneumococcal conjugated vaccines (PCVs); efficacy and effectiveness; immunocompromised; immunogenicity; older adults.