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

Background: 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.

Methods: 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.

Results: 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 (<8 & <64) showed significant increases in OI fold raise across all tested serotypes post-vaccination. This robust immune response was consistent across serotypes, indicating highly effective seroconversion in individuals with low baseline antibody levels.

Conclusion: 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.