Evaluating patient immunocompetence through antibody response to pneumococcal polysaccharide vaccine using a newly developed 23 serotype multiplexed assay

Assessing T-cell independent antibody response to polysaccharide vaccines is crucial for diagnosing humoral immune deficiencies. However, immunocompetence criteria based on S. pneumoniae vaccination remain unclear. We evaluated IgG antibody vaccine response in healthy individuals to establish interpretive criteria. Pre- and 4-week post-vaccination sera were collected from 79 adults. Antibody concentrations to PNEUMOVAX 23 serotypes were measured using a multiplexed platform. Immunocompetence was determined by fold increase in post-vaccination response, percentage of serotypes achieving 4- or 2-fold antibody ratio, and post-vaccination concentration ≥ 1.3 μg/mL. Immunogenicity varied widely across the 23 serotypes (26.6% to 94.9% for ≥4-fold increase, 51.9% to 98.7% for ≥2-fold increase). Immunocompetence based on historic criteria of ≥4-fold increase in antibody ratio to ≥70% of serotypes was low (72.2%), but increased to 98.7% with criteria of at least a 2-fold increase and/or post-vaccination concentration ≥ 1.3 μg/mL. Current criteria for assessing immunocompetence may be overly stringent and require updating.