ABSTRACT
Influenza viruses, respiratory syncytial virus (RSV), and SARS-COV2 are among the most dangerous respiratory viruses. Zinc is one of the essential micronutrients and is very important in the immune system. The aim of this narrative review is to review the most interesting findings about the importance of zinc in the anti-viral immune response in the respiratory tract and defense against influenza, RSV, and SARS-COV2 infections. The most interesting findings on the role of zinc in regulating immunity in the respiratory tract and the relationship between zinc and acute respiratory distress syndrome (ARDS) are reviewed, as well. Besides, current findings regarding the relationship between zinc and the effectiveness of respiratory viruses' vaccines are reviewed. The results of reviewed studies have shown that zinc and some zinc-dependent proteins are involved in anti-viral defense and immune regulation in the respiratory tract. It seems that zinc can reduce the viral titer following influenza infection. Zinc may reduce RSV burden in the lungs. Zinc can be effective in reducing the duration of viral pneumonia symptoms. Zinc may enhance the effectiveness of hydroxychloroquine in reducing mortality rate in COVID-19 patients. Besides, zinc has a positive effect in preventing ARDS and ventilator-induced lung damage. The relationship between zinc levels and the effectiveness of respiratory viruses' vaccines, especially influenza vaccines, is still unclear, and the findings are somewhat contradictory. In conclusion, zinc has anti-viral properties and is important in defending against respiratory viral infections and regulating the immune response in the respiratory tract.