Does the COVID-19 cytokine storm exist? Cytokines play a crucial role in the immune response. If this immune response is too strong, also known as 'cytokine storm', it can cause harm to the patient. Following the measurement of several important cytokines in patients with COVID-19 and various other severe diseases, researchers show that COVID-19 is not characterized by a cytokine storm. This may have consequences for the treatment of these patients, the researchers write. Source 9x.