Any viral infection leads to a decrease in lymphocyte levels but the change varies from virus to virus. In the case of COVID-19, it has been found out that CD8+ cells (Cytotoxic T cells) play an important role in predicting the severity of the infection and therefore are crucial in designing a proper treatment method. It has been observed that the levels of CD4+ and CD8+ cells decrease drastically in severe cases but not so much in milder ones. Even though a change in CD4+ to CD8+ ratio is not seen. It was observed that the CD4+ and CD8+ levels start rising as the body responds to treatment.