This 2020 review highlighted earlier clinical data on zinc:
“Zinc is known to modulate antiviral and antibacterial immunity and regulate inflammatory response.
Zinc possesses anti-inflammatory activity by inhibiting NF-κB signaling and modulation of regulatory T-cell functions.
The most critical role of zinc is demonstrated for the immune system.
Zinc regulates proliferation, differentiation, maturation, and functioning of leukocytes and lymphocytes.
Alteration of zinc status significantly affects immune response resulting in increased susceptibility to inflammatory and infectious diseases including acquired immune deficiency syndrome, measles, malaria, tuberculosis, and pneumonia. Zinc status is associated with the prevalence of respiratory tract infections in children and adults.
In view of the high prevalence of zinc deficiency worldwide (up to 17%), its impact on population health is considered as a significant issue. Certain groups of people, including infants, especially preterm ones, and elderly, are considered to be at high risk of zinc deficiency and its adverse effects.
Zinc was shown to have a significant impact on viral infections through modulation of viral particle entry, fusion, replication, viral protein translation and further release for a number of viruses including those involved in respiratory system pathology. Increasing intracellular Zn levels through application of Zn ionophores significantly alters replication of picornavirus, the leading cause of common cold.
The results of systematic analysis confirmed the efficiency of intake of at least 75 mg/day Zn in reduction of pneumonia symptom duration but not severity, with the response being more pronounced in adults than in children.”