CRP and COVID-19: We chose the following studies for this review: (1) study subjects: people who have been diagnosed with COVID-19; (2) nVNS as the experimental arm; (3) sham nVNS or standard of care as a means of comparison; (4) at least one biomarker was reported in the study, such as C-reactive protein (CRP), IL-6, IL-10, cortisol, fibrinogen, and D-dimer; and (5) RCTs.