Robust SARS-COV-2-specific T-cell immune memory persists long-term in immunocompetent individuals post BNT162b2 double shot

BACKGROUND: A robust efficiency of mRNA vaccines against coronavirus disease-2019 has been demonstrated, however, the intended long-term protection against SARS-CoV-2 has been challenged by the waning humoral and cellular immunity over time, leading to a third vaccination dose recommendation for immunocompetent individuals, six months after completion of primary mRNA vaccination. METHODS: We here measured humoral responses via an immunoassay measuring SARS-CoV-2 neutralizing antibodies and T-cell responses using Elispot for interferon-γ 1- and 8- months post full BNT162b2 vaccination, in 10 health-care professionals. To explore whether the declining abundance of coronavirus-specific T-cells (CoV-2-STs) truly reflects decreased capacity for viral control, rather than the attenuating viral stimulus over time, we modeled ex vivo the T-cellular response upon viral challenge in fully vaccinated immunocompetent individuals, 1- and 8-months post BNT162b2. FINDINGS. Notwithstanding the declining CoV-2-neutralizing antibodies and CoV-2-STs, re-challenged CoV-2-STs, 1- and 8-months post vaccination, presented similar functional characteristics including high cytotoxicity against both the unmutated virus and the delta variant. INTERPRETATION. These findings suggest robust and sustained cellular immune response upon SARS-CοV-2 antigen exposure, 8 months post mRNA vaccination, despite declining CοV-2-STs over time in the presence of an attenuating viral stimulus.