Statistics
Flow cytometry data were analyzed using FlowJo version 10.6.2 (BD
Biosciences); gating strategy is presented in figures S1. For the
analysis of SARS-CoV-2 reactive T cells, a threshold of 0.01% was
employed to define a detectable response. Single stains and
fluorescence-minus-one controls were used for gating. Gates of each
study participant were adjusted according to the negative control. CD4+
T cells expressing CD154 and CD137 and CD8+ T cells expressing CD137
were defined as reactive T cells. Statistical analysis was performed
using GraphPad Prism v7. Categorical variables are summarized as numbers
and frequencies; quantitative variables are reported as median and
interquartile range. Normality tests were performed with the
Shapiro-Wilk Test. All applied statistical tests are two-sided.
Kruskal-Wallis Test and Mann-Whitney-Test were applied to perform
comparisons. The age between the two cohorts was compared using unpaired
two-tailed t-test, and gender was compared using two-tailed Fisher’s
exact test. Correlational relationships were explored with Spearman´s
test. p values below 0.05 were considered significant; only significant
p values are reported in the figures. p values were not corrected for
multiple testing, as this study was of an exploratory nature.