Adults with low opsonic natural antibody levels against Streptococcus pneumoniae show enhanced response to PPSV23 vaccination

Pneumococcal diseases pose a significant public health concern globally, particularly among young children and the elderly. Vaccination plays a crucial role in their prevention. This study evaluated the functional immune responses to Pneumococcal polysaccharide vaccine serotypes in healthy Indian adults before and after administering a single dose of PPSV23 immunization. A total of 125 healthy participants aged 18–65 received the PPSV23 vaccine, and their pre- and post-immunization sera were analyzed by MOPA. Opsonic Index, Geometric mean OPA titers and fold increase for each serotype was calculated. The highest baseline OPA GMTs were observed for serotypes 33F,17F,9N,20, and 6B. The lowest OPA GMTs were noted against types 1 and 12F. OPA GMTs post-vaccination increased significantly for all serotypes, with geometric mean fold rise (GMFR) ranging from 4.3 to 267.5. Participants with low pre-immunization OPA titers ( The PPSV23 vaccine elicits a strong immunogenic response in individuals with low pre-immunization OPA titers, achieving substantial increases in opsonic index fold raise across various serotypes.