Pneumococcal conjugate vaccines in older adults and immunocompromised individuals

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.