Stabilizers are used to help vaccines maintain their effectiveness during storage. Vaccine stability is important because vaccines must be transported and stored for periods of time. Compounds called additives, including stabilizer ingredients, ensure that vaccines remain safe and effective during storage. Here are some examples of additive ingredients in flu vaccine:
Gelatin is a stabilizer in some vaccines that protects against damage from heat or freeze-drying for storage. Sugars, artificial sweeteners, and MSG also may be used to keep some vaccines stable and effective.
Other possible stabilizers include an amino acid called glycine or a protein in blood called albumin.
All stabilizers used in vaccines occur naturally in the body or are substances people encounter in everyday life. There may also be tiny amounts of substances left over from the process of manufacturing the vaccine:
Tiny amounts of egg protein might remain in a vaccine after scientists grew the virus in eggs in a lab.