Fig. 2. Immune control of SARS-CoV-2 reinfection.

Immune memory could function to control severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection at several stages. Residual levels of neutralizing antibodies may block the entry of virus into host cells or prevent the early dissemination of virus. Even if viral growth is established, residual antibody and cellular responses may function to slow viral growth, providing a longer window of time for the action of recall immune responses. Recall responses start to take effect later in infection, boosting immune-mediated control and reducing the virus to low levels. Depending on the timing and efficacy of immune control, infection may vary from undetectable or mild, through to severe infection with viral detection and immune boosting.