Salt, specifically sodium chloride (NaCl), is the most common and essential salt used in chemical industries, food production and medical applications. This review extensively looked into the use of salt in medical applications and the development of vaccines, including the recently developed SARS-CoV-2 vaccine. This review also discussed several salt-producing systems to further understand the source of salt. This study focused on several main fields of medical use of salt: saline solution content, respiratory filtration, hyponatremia, ophthalmology, dermatology, and vaccine development studies. Several studies identified that NaCl could deactivate viruses as observed, NaCl is part of the COVID-19 vaccine excipient for Pfizer-BioNTech and AstraZeneca. Further applications of sodium chloride should be explored due to its various advantages in the medical field.