CD4 and tetanus: Upon vaccination against diseases like tetanus and influenza, CD4+ cells are activated and begin to proliferate in humans [25] In our study, an increase in the percentage of CD4+, CD8+, CD4 + FoxP3+, and CD8 + FoxP3+ cells 1 month after vaccination suggests a robust immune activation, with CD4+ and CD8+ cells representing helper and cytotoxic T cell responses, respectively, and CD4 + FoxP3+ and CD8 + FoxP3+ cells indicating regulatory T cells (Tregs) that help modulate the immune response.