Thesis title: Evaluation of Antibodies Against SARS-CoV-2 in a Vaccinated Population
This study examines the humoral immune response to SARS-CoV-2 in a cohort of 295 vaccinated individuals, including military and civilian personnel, vaccinated with Comirnaty-BioNTech/Pfizer. Conducted at the Scientific Department of Rome’s "Celio" Military Polyclinic, the study collected a total of 885 serum samples at three critical time points: pre-vaccination (T0), post-first dose (T1), and post-second dose (T2), representing peak immunogenicity. Neutralizing antibody titers were measured using the gold-standard Plaque Reduction Neutralization Test (PRNT) and compared with titers from the high-throughput LIAISON® SARS-CoV-2 TrimericS IgG assay, focusing on responses against SARS-CoV-2 variants B.1 (Codogno), B.1.1.7 (Alpha), and XBB.1.16.11 (Omicron).
The analysis revealed that, at T2, PRNT50 titers varied widely, with a majority of patients reaching titers between 1:80 and 1:10240, reflecting substantial inter-individual variability in neutralizing responses. The concordance between PRNT and the LIAISON® assay was high at PRNT50 titers up to 1:80, confirming the CLIA-based platform's reliability for routine, large-scale antibody quantification. However, at higher antibody concentrations, the assays displayed divergence, particularly with high PRNT titers (≥1:1280), suggesting that while the LIAISON® assay is suitable for general monitoring, PRNT remains essential for precise quantification in cases of robust immunogenicity. Variant-specific analysis demonstrated that the B.1 variant elicited the strongest neutralizing response, while the Alpha (B.1.1.7) variant displayed moderate titers, aligning with its prevalent circulation during initial vaccine rollout. Conversely, the Omicron sublineage XBB.1.16.11 exhibited significantly lower neutralizing titers, indicating partial immune escape, which may limit vaccine efficacy against this and similar emerging variants.
The findings underscore the effectiveness of Comirnaty in generating strong neutralizing antibody responses, particularly against earlier SARS-CoV-2 strains. However, the reduced response to the Omicron XBB.1.16.11 variant highlights the ongoing challenge of variant-driven immune evasion and supports the necessity for continuous genomic surveillance and possible vaccine updates to maintain robust population immunity. The integration of high-throughput assays like the LIAISON® SARS-CoV-2 TrimericS IgG assay in public health monitoring frameworks could significantly enhance the efficiency of immunity tracking, aiding in timely adjustments to vaccination strategies and booster campaigns to address variant-specific immune challenges.