International Journal of Scientific Research and Engineering Development

Post-vaccination immune persistence varies significantly across booster regimens, particularly between homologous (e.g., mRNA/mRNA) and heterologous (e.g., VV/mRNA) strategies. This heterogeneity poses challenges for public health planning and long-term immunity forecasting. In this study, we developed a novel statistical framework integrating Bayesian survival analysis with linear mixed-effects regression to jointly model longitudinal IgG dynamics and time-to-waning of protective immunity in a cohort of 334 individuals—206 previously infected and 128 infection-naïve—from real-world data collected between December 2022 and September 2023. Plasma optical density (OD) values from ELISA assays served as a proxy for anti-SARS-CoV2 IgG levels. Participants were categorized by booster type (homologous vs. heterologous), prior infection status, and number of doses (2–4). Our integrated model revealed that heterologous boosting was associated with significantly slower IgG decay (hazard ratio HR = 0.62, 95% credible interval [0.48–0.79]) compared to homologous regimens. Moreover, prior SARS-CoV-2 infection independently enhanced both humoral and cellular immune persistence, with infected individuals showing 1.8-fold higher median OD values at 6+ months post-boost. The joint modeling approach successfully captured inter-individual variability through random slopes and intercepts while accounting for censoring in immune waning via a Weibull-based survival component. This framework provides a flexible, predictive tool for evaluating future booster strategies—not only for SARS-CoV-2 but also for other pathogens requiring durable immunity. Our findings support the immunological advantage of heterologous prime-boost schedules, especially when combined with natural infection, and underscore the value of methodological integration in longitudinal immunology research.

Mohammedelameen E. Qurashi, Amal E. Y. Hagsddig,"Bayesian Survival and Mixed-Effects Modeling of Immune Persistence Under COVID-19 Boosting" International Journal of Scientific Research and Engineering Development, V9(3): Page(2336-2350) May-June 2026. ISSN: 2581-7175. www.ijsred.com. Published by Scientific and Academic Research Publishing.