CD4 and COVID-19: In the influenza vaccine cohort, the time course of T lymphocytes during the study was quite similar to changes observed in the COVID-19 vaccine cohort, with increases in the CD4+T cell count at the end of the study as compared with baseline, both in the ABB C1® supplement group and in the placebo group, although the magnitude of the increase was somewhat greater in the ABB C1® group (Figure 3).