Which substance is a preservative used in some vaccines?

Which substance is a preservative used in some vaccines?

• A. Sodium chloride
• B. Thimerosal
• C. Water
• D. Glucose

Answer: (B)

Preservatives in vaccines protect the product from microbial contamination once a vial is opened or stored for use, especially in multidose vials. Thimerosal is a mercury-containing compound that has been used as such a preservative in some vaccines to prevent growth of bacteria or fungi. It works by inhibiting microbes that could enter the vial during repeated needle punctures, allowing multiple doses to be drawn safely. The other substances listed are not preservatives: sodium chloride is a salt used to make the solution isotonic, water is the diluent, and glucose can serve as stabilizer or energy source in some formulations. In modern practice, many vaccines are preservative-free, and when thimerosal is present, it is in very small, tightly regulated amounts.

Preservatives in vaccines protect the product from microbial contamination once a vial is opened or stored for use, especially in multidose vials. Thimerosal is a mercury-containing compound that has been used as such a preservative in some vaccines to prevent growth of bacteria or fungi. It works by inhibiting microbes that could enter the vial during repeated needle punctures, allowing multiple doses to be drawn safely. The other substances listed are not preservatives: sodium chloride is a salt used to make the solution isotonic, water is the diluent, and glucose can serve as stabilizer or energy source in some formulations. In modern practice, many vaccines are preservative-free, and when thimerosal is present, it is in very small, tightly regulated amounts.