Use

Measurement of IgG antibodies to 13 Streptococcus pneumoniae serotypes is used to estimate pre‑existing antibody levels and to assess immunologic response after pneumococcal vaccination. Serologic correlates of protection are variably established; protective levels are thought to range from ≥0.3‑0.50 µg/mL in healthy children, with higher thresholds (≥1.3 µg/mL) considered in immunocompromised individuals. Interpretation also considers antibody avidity and opsonophagocytic activity; post‑vaccination response is often defined by seroconversion or a 2‑ to 4‑fold rise in IgG titers in a majority of measured serotypes.