Common Vaccine Ingredients
There are several important ingredients found in vaccines in addition to the microorganism component.
Stabilizers
Stabilizers, including sugars and gelatin, are included to help to ensure that the vaccine is effective from manufacturing to administration.
Cell Culture Components
To obtain an adequate amount of antigen for a vaccine, the microorganisms of interest are often grown under controlled conditions. After manufacturing, some vaccines may still contain nutrients or materials used for growing the microorganism. For example, the yellow fever and influenza viruses are grown in eggs, therefore, these vaccines may contain egg protein.
Inactivating Ingredients
Vaccines frequently contain small amounts of formaldehyde and antibiotics to prevent the vaccine from being contaminated with other viruses or bacteria during processing and administration. It is important to note that humans produce formaldehyde naturally and can break down the formaldehyde produced in the body, as well as formaldehyde absorbed from the environment. For this reason, the amount of formaldehyde present in vaccines is usually not significant enough to make someone ill. In fact, the United States Food and Drug Administration reports that a newborn produces 50 to 70 times more formaldehyde in their body than they would ever receive in a single dose of a vaccine.
Adjuvants
Killed and subunit vaccines can sometimes cause the body to generate a weaker immune response than would be produced with a live vaccine. To improve the efficacy of vaccines, components are often added to help stimulate the immune system and improve the overall immune response. These components are known as adjuvants. Adjuvants are often substrates for pattern recognition receptors and can be covalently linked to an antigen when included in vaccines. Adjuvants improve the immune response by helping increase the number of antibodies produced, assisting in the recruitment of dendritic cells, and improving immune memory. Adjuvants can also accelerate the immune response and allow for less antigen and fewer doses to achieve the same desired immune response. These implications are especially crucial in pandemic situations when a large number of vaccine doses are needed in a short period of time.