Humoral response during the COVID-19 pandemic: from infection to vaccination

Promoters

Prof. Jonathan DOUXFILS & Prof. Jean-Michel DOGNE, UNamur, Department of pharmacy, Research Unit in Clinical Pharmacology and Toxicology (URPC) 

Jury

• Prof. Jonathan Douxfils (Academic Promotor, UNamur, Belgium)
• Prof. Jean-Michel Dogné (Academic Promotor, UNamur, Belgium)
• Prof. Nicolas Dauby (CHU Saint-Pierre, Belgium)
• Dr. Isabelle Desombere (Sciensano, Belgium)
• Prof. Nicolas Franco (UNamur, Belgium)
• Prof. Damien Gruson (UCLouvain, Cliniques Universitaires Saint-Luc, Belgium)
• Prof. Mario Plebani (University of Padova, Italy)

Summary

COVID-19 is an infectious disease caused by the SARS-CoV-2. COVID-19 was swiftly declared a pandemic by the World Health Organization on March 11, 2020.

Early in the pandemic, the healthcare community witnessed the introduction of a myriad of commercial assays designed to measure binding antibodies. The role of neutralizing antibodies as the best correlate of protection against SARS-CoV-2 infection was quickly highlighted. A pseudovirus-neutralization test was therefore developed by our team and compared with several binding tests.

Major efforts have been made to produce and clinically validate new COVID-19 vaccines at an unprecedented speed. The CRO-VAX HCP study was designed to evaluate the humoral response among healthcare professionals having received two doses of COVID-19 BNT162b2 vaccine.

Given the decrease of vaccine efficacy over time and the emergence of variants that can escape immunity, a third dose was soon recommended by the authorities. This booster was administered to 155 volunteers in the CRO-VAX HCP study.

Still facing a decline in vaccine efficacy, a second adapted booster was proposed. On September 2022, 54 participants of the CRO-VAX HCP study received this second booster. The humoral response was evaluated and neutralizing antibodies against several variants were measured. Moreover, we also measured the cellular response using an interferon-gamma release assay. As compared to the humoral response, which declined considerably over time, the cellular response remained quite stable. This could therefore explain why individuals with low antibody titers may still be protected against a severe form of the disease.