The requirement for preservatives in vaccines arose from many incidents in the early 20th century of children who developed severe and occasionally fatal bacterial infections after administration of vaccines contained in multi-dose vials. For example, in 1916, four children died, 26 developed local abscesses, and 68 developed severe systemic infections after receipt of a typhoid vaccine contaminated with the bacteria Staphylococcus aureus. Therefore, preservatives are required in some vaccines to prevent bacterial or fungal contamination. However, not all vaccines contain preservatives. If a vaccine is given as a single dose, it may not contain any preservatives. But some are delivered in larger vials, designed for multiple shots. Since multi-dose liquid vaccines may be penetrated by a needle through a rubber bundle many times over a long period of time. In this case, bacteria or fungi can enter the vial. Receiving a vaccine contaminated with bacteria or fungi can be dangerous. Preservatives are therefore needed to reduce the probability of the risk occurring. It is important to note that preservatives are carefully regulated and are subject to special scrutiny from time to time.
Common preservatives in vaccines
Preservatives are needed to prevent contamination of multi-dose vials each time individual doses are drawn. The most common types of preservatives used in liquid vaccines are shown below.
2-Phenoxyethanol is an organic chemical compound that is used in vaccines. It is currently used as a preservative in a Food and Drug Administration-approved available vaccine, IPOL, for the prevention of polio, at a concentration of 0.5%. It is metabolized (broken down) and excreted through exhalation, urine and feces and is of minimal toxicity to humans. It is one of the most commonly used vaccine preservatives.
Figure 1. Chemical structure of 2-phenoxyethanol
Benzethonium chloride is a chemical that has antimicrobial and antiseptic properties. This preservative is currently used in only one Food and Drug Administration-approved vaccine, BioThrax, for the prevention of disease caused by Bacillus anthracis.
Figure 2. Chemical structure of benzethonium chloride
The thimerosal (an organomercury compound) has been extensively used as a vaccine preservative for more than 80 years. The antimicrobial properties of thimerosal contribute to the safe use of vaccines in multi-dose vials, and the ability to package certain vaccines, such as those for seasonal and pandemic influenza, in multi-dose vials helps facilitate immunization campaigns in the globally that save lives. However, the use of thimerosal as a preservative in U.S. Food and Drug Administration-licensed vaccines has significantly declined due to controversy over the safety of thimerosal.
Figure 3. Chemical structure of thimerosal
Phenol is an aromatic alcohol used as a preservative in vaccines. Phenol is currently a preservative for three existing vaccines approved by the Food and Drug Administration. These three vaccines are Pneumovax 23 (for prevention of pneumococcal disease caused by the 23 serotypes contained in the vaccine) and Typhim Vi (for prevention of typhoid fever) and ACAM2000 (for prevention of smallpox). All of these vaccines contain 0.25% phenol.
Figure 4. Chemical structure of phenol
What we offer
Alfa Chemistry supplies preservatives to companies researching vaccines. If you cannot find the preservative you need, please contact us. We also offer product customization according to customer's detailed requirements.
Our products and services are for research use only and cannot be used for any clinical purposes.