The frequencies of epitope-specific CD8+ T cells were decreased in the individuals receiving two doses of SARS-CoV-2 vaccination than only one dose
The frequencies of epitope-specific CD8+ T cells in individuals who received only one dose of Ad5-nCoV vaccine were further analyzed according to the time interval between the latest vaccination and sample collection. The results showed that the frequencies of epitope-specific CD8+ T cells were elevated from the time less than 30 days to the time 30 days-60 days, then decreased at the time 60 days-90 days, and again elevated at the time 90 days-120 days, even more than 120 days. The trends of the frequencies of epitope-specific CD8+ T cells at different time quantum was similar between the epitope S7 and epitope S9 (Figure 4A-4B). Then we compared the frequencies of epitope-specific CD8+ T cells in individuals who received different doses of Ad5-nCoV vaccination. Notably, the frequencies of epitope-specific CD8+ T cells in subjects with two doses vaccination were lower compared with that in subjects with only one dose vaccination (P <0.05 for epitope S7) (Figure 4C-4D).