Humoral and cellular response three months following bivalent booster administration

Abstract Studies about the evaluation of the humoral and cellular response following the bivalent booster administration are still scarce. The aim of this study was to assess the humoral and cellular response in a cohort of healthcare workers that received either the BA.1 or the BA.4/5 bivalent booster. Blood samples from participants were collected before the administration of either the BA.1 or BA.4/5 bivalent booster from Pfizer-BioNTech and after 14, 28, and 90 days. The humoral response was evaluated using neutralizing antibodies against the BA.5 Omicron variant and binding total and IgG antibodies. The cellular response was assessed by measurement of the release of interferon gamma (IFNγ) from T cells in response to an in vitro SARS-CoV-2 stimulation. Although most participants still had a robust cellular response before the booster, a significant increase in the cellular response was observed after 2 weeks, especially in participants presenting lower levels of IFNγ before the booster administration. Levels of IFNγ remained stable at 3 months and contrast sharply with the rapid decrease of BA.5-specific neutralizing antibodies. Binding antibodies were only modestly correlated to the neutralizing capacity. The evolution of the humoral and cellular response was non-significantly different between participants that received the BA.1 or the BA.4/5 bivalent booster. The monitoring of the humoral and cellular response could be useful to identify patients with a poor adapted immunity that would need to benefit first from an additional booster shot.