Lymphopenia is a health condition in which people have low white blood cell count in their blood. Without these cells, the body is unable to defend itself effectively against pathogens. Lymphopenia is one type of way your body can be immunocompromised; it can be caused by many things, including infections, inherited conditions, autoimmune disorders, and nutritional deficiencies. Earlier in the pandemic, scientists learned that some patients can develop lymphopenia from SARS-CoV-2 infection — but there’s been little research into it since. Although this condition is more rarely seen in COVID-19 as compared to HIV/AIDS, some advocates have suggested the two diseases are similar in their damage to the immune system.