Understanding the functioning and dynamics of the immune system becomes important given the role that it plays in fighting off infection and disease. In this study, a stochastic version of the immune response model have been developed and analysed. In this work, the Fokker-Planck equation has been derived, which is then used to compute the joint probability distribution of T cells and virus particles by making use of the Wilemski-Fixman approximation. This approach allows to obtain analytical solutions of the probability distribution functions and the average virus particles in the limit of short and long times, showing how the infection begins and ends. Carried out a comparison with the available SARS-CoV-2 virus data from patients in Germany. At short times, i.e., during the early period of infection, the model predicts that there is a steep rise in the virus levels with time, whereas, at long times, the virus levels drop gradually, in accordance with the model's prediction.