The results of the present study demonstrated that the absolute counts were significantly lower in the peripheral blood of COVID-19 patients for the following lymphocyte populations; total lymphocytes (Figure 2A, p < 0.001), CD3+ T lymphocytes (Figure 2A, p < 0.001), CD4+ T lymphocytes (Figure 2A, p < 0.001), CD8+ T lymphocytes (Figure 2A, p < 0.001), CD19+ B lymphocytes (Figure 2A, p < 0.001), and CD16+CD56+ natural killer cells (Figure 2A, p = 0.041 vs the HS and p<0.001 vs VS) compared to both the healthy subjects (HS) and vaccinated subjects (VS). Here, CD4 is linked to COVID-19.