Why the elderly appear to be more severely affected by COVID-19: The potential role of immunosenescence and CMV.

The significantly higher mortality rates seen in the elderly compared with young children during the coronavirus disease 2019 (Covid-19) pandemic is likely to be driven in part by an impaired immune response in older individuals. Cytomegalovirus (CMV) seroprevalence approaches 80% in the elderly. CMV has been shown to accelerate immune ageing by affecting peripheral blood T cell phenotypes and increasing inflammatory mediated cytokines such as IL-6. The elderly with pre-existing but clinically silent CMV infection may therefore be particularly susceptible to severe Covid-19 disease and succumb to a cytokine storm which may have been promoted by CMV. Here, we evaluate the potential role of CMV in those with severe Covid-19 disease and consider how this relationship can be investigated in current research studies.