Does the immune response to prior CMV infection determine the immune response to SARS-CoV 2?

Infection with SARS-CoV 2 is asymptomatic in 40-50% cases, but severe in ~10%. Why this dramatic difference in outcomes? Most viral infections are controlled by ‘cytotoxic T cells’, which kill infected cells. Patients with mild disease have robust T cell responses to the virus. But in those with severe disease, the T cell response is consistently sub-optimal and at 7-10 days the T cells develop markers of exhaustion and senescence. At this point the virus escapes control and severe disease ensues. The best documented associations of severe disease are age and male sex: indeed, T cell responses are poorer in older individuals and males. It is also known that prior infection with a virus called cytomegalovirus (CMV) has a major impact on T cells, and healthcare workers from ethnic minorities suffer severe COVID-19 more often and have been infected with CMV more often and earlier. We will assess rates of prior infection with CMV in patients with severe COVID-19. If we can show that the ~50% of the population who have never had CMV are less likely or resistant to severe COVID-19, then this may help offer a viable way out of the economic problems of a prolonged lockdown.