SARS‐CoV‐2‐Spike T‐cell response after receiving one or two Wuhan‐Hu‐1‐based mRNA COVID‐19 vaccine booster doses in elderly nursing home residents

Abstract

AbstractThe effect of COVID‐19 booster vaccination on SARS‐CoV‐2 T‐cell mediated immune responses in elderly nursing home residents has not been explored in depth. Thirty‐nine elderly nursing home residents (median age, 91 years) were included, all fully vaccinated with mRNA vaccines. The frequency of and the integrated mean fluorescence (iMFI) for peripheral blood SARS‐CoV‐2‐Spike reactive IFN‐γ‐producing CD4+ or CD8+ T cells before and after the first (Pre‐3D and Post‐3D) and second (Pre‐4D and Post‐4D) vaccine booster doses was determined using flow cytometry for an intracellular staining method. 3D increased significantly (p = 0.01) the percentage of participants displaying detectable SARS‐CoV‐2‐T‐cell responses compared with pre‐3D (97% vs. 74%). The magnitude of the increase was statistically significant for CD8+ T cells (p = 0.007) but not for CD4+ T cells (p = 0.77). A trend towards higher frequencies of peripheral blood SARS‐CoV‐2‐CD8+ T cells was observed post‐3D compared with pre‐3D (p = 0.06). The percentage of participants with detectable SARS‐S‐CoV‐2 CD4+ T‐cell responses decreased post‐4D (p = 0.035). Following 4D, a nonsignificant decrease in the frequencies of both T cell subsets was noticed (p = 0.94 for CD8+ T cells and p = 0.06 for CD4+ T cells). iMFI data mirrored that of T‐cell frequencies. The kinetics of SARS‐CoV‐2 CD8+ and CD4+ T cells following receipt of 3D and 4D were comparable across SARS‐CoV‐2‐experienced and ‐naïve participants and between individuals receiving a homologous or heterologous vaccine booster. 3D increased the percentage of elderly nursing home residents displaying detectable SARS‐CoV‐2 T‐cell responses but had a marginal effect on T‐cell frequencies. The impact of 4D on SARS‐CoV‐2 T‐cell responses was negligible; whether this was due to suboptimal priming or rapid waning could not be ascertained.