What is convalescent plasma? Does it help people with COVID-19?

When people recover from COVID-19, their blood contains antibodies that their bodies produced to fight the coronavirus and help them get well. Antibodies are found in plasma, a component of blood. Convalescent plasma — literally plasma from recovered patients — has been used for more than 100 years to treat a variety of illnesses from measles to polio, chickenpox, and SARS. It is widely believed to be safe. In the current situation, antibody-containing plasma from a recovered patient is given by transfusion to a patient who is suffering from COVID-19. The donor antibodies may help the patient fight the illness, possibly shortening the length or reducing the severity of the disease. Though convalescent plasma has been used for many years, and with varying success, not much is known about how effective it is for treating COVID-19. A recent analysis of 35,000 hospitalized patients who received convalescent plasma to treat severe COVID-19 suggests that the therapy may reduce the risk of dying. The data comes from the ongoing Expanded Access Program (EAP) led by the Mayo Clinic. The researchers found that patients with (or at risk of) severe COVID-19 who received convalescent plasma within three days of diagnosis were less likely to die than patients who received convalescent plasma later in their illness. The problem? The study has no control group. All patients who are eligible to get convalescent plasma under the EAP receive that treatment. As a result, questions remain as to whether, or the degree to which, convalescent plasma is effective for treating COVID-19; who would benefit from this treatment; and when in the course of illness convalescent plasma is most effective. (High demand to enroll in the program may have also unintentionally driven down enrollment in randomized, controlled studies of convalescent plasma across the country.) Despite this, the FDA has issued an emergency use authorization (EUA) for convalescent plasma, which will make it easier for hospitals to provide the treatment to their patients.