Zinc gluconate and ascorbic acid (vitamin C) are commonly available over-the-counter supplements that patients have been taking as over-the-counter supplements to treat viral illnesses. 

Considering the latency of the disease and prolonged incubation period, even patients who present with mild symptoms may progress to requiring hospitalization, prescription medication therapy, mechanical ventilation, and/or death. Zinc is known to increase polymorphonuclear cells’ ability to fight infection, and ascorbic acid is an antioxidant that may be beneficial in the immune response. Some evidence suggests that high doses of ascorbic acid and zinc gluconate may lower the duration of common cold symptoms and reduce the severity of symptoms. 

Zinc is known to play a role in immune function through antibody and white blood cell production. There is evidence to show that zinc deficiency increases pro-inflammatory cytokines and reduces the production of antibodies. The role of zinc is also shown in coronavirus biology. Additionally, studies on SARS have shown that zinc can also inhibit ribonucleic acid polymerase. Ascorbic acid is a known antioxidant, and many studies have suggested that it can affect the immune system. Human trials have also reported that ascorbic acid may reduce susceptibility to viral respiratory infections and pneumonia. 

Reference: Thomas S, Patel D, Bittel B, et al. JAMA Network Open. 2021; 4: e210369.