COVID-19 is an infectious disease caused by SARS-CoV-2. COVID-19 was quickly declared a pandemic by the World Health Organization (WHO) on March 11, 2020.
At the start of the pandemic, healthcare professionals were faced with the marketing of numerous kits 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 neutralization assay with the use of pseudovirus was therefore developed by our team and compared with several binding assays.
There have been considerable efforts to produce and clinically validate new vaccines against COVID-19. The CRO-VAX HCP study was designed to assess the humoral response in a population of healthcare professionals who had received two doses of COVID-19 BNT162b2 vaccine.
Given the decline in vaccine efficacy over time and the emergence of variants likely to evade immunity, a third dose was quickly recommended by the authorities to boost immunity. This was administered to 155 volunteers in the CRO-VAX HCP study.
Still facing a decline in vaccine efficacy over time and the emergence of new variants, a second adapted booster was proposed. In September 2022, 54 participants in the CRO-VAX HCP study received this second booster. The humoral response was assessed and neutralizing antibodies against several variants were measured. In addition, we also measured the cellular response using an interferon-gamma release assay. Compared with the humoral response, which declines considerably over time, the cellular response remained fairly stable. This could therefore explain why individuals with low antibody titers can still be protected against a severe form of the disease
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