Table 1.

Keyword combinations used in the search for articles^*

1	Zinc AND (COVID-19 or 2019 novel coronavirus disease or COVID19 or COVID-19 pandemic or SARS-CoV-2 infection or COVID-19 virus disease or 2019 novel coronavirus infection or 2019-nCoV infection or coronavirus disease 2019 or coronavirus disease-19 or 2019-nCoV disease or COVID-19 virus infection)
2	Zinc AND (Antiviral Agents or Agents, Antiviral or Antivirals or Antiviral Drugs or Drugs, Antiviral) AND (Respiratory Tract Infections or Infection, Respiratory Tract or Respiratory Tract Infection or Infections, Respiratory or Respiratory Infections or Infections, Respiratory Tract or Upper Respiratory Tract Infections or Infections, Upper Respiratory Tract or Infections, Upper Respiratory or Respiratory Infection, Upper or Upper Respiratory Infection)
3	Zinc AND (Immunologic Factors or Immune Factors or Factors, Immune or Immunological Factors or Factors, Immunological or Factors, Immunologic or Immunomodulators or Biological Response Modifiers or Biomodulators or Modifiers, Biological Response or Response Modifiers, Biological) AND (Respiratory Tract Infections or Infection, Respiratory Tract or Respiratory Tract Infection or Infections, Respiratory or Respiratory Infections or Infections, Respiratory Tract or Upper Respiratory Tract Infections or Infections, Upper Respiratory Tract or Infections, Upper Respiratory or Respiratory Infection, Upper or Upper Respiratory Infection)

^*Since the most articles included in this review were published before the COVID-19 pandemic, articles related to other respiratory diseases were included for a better understanding of involved mechanisms.