Adjuvants and Other Vaccine Ingredients
In addition to antigens that alert the immune system to an infectious agent, vaccines may also contain substances called adjuvants, which improve the immune response produced by the vaccines. Currently, the only adjuvant licensed for human use in the United States is an “alum” adjuvant, which is composed of aluminum salts.
Adjuvants do a variety of things: they can bind to the immune-inducing antigens in the vaccine, help keep antigens at the site of injection, and help deliver antigens to the lymph nodes, where immune responses to the antigens are initiated. The slowed release of antigens to tissue around the injection site and the improved delivery of antigens to the lymph nodes can produce a stronger antibody response than the antigen alone.
In 2008, NIAID-supported researchers advanced the adjuvant field by discovering how alum helps vaccines provide protection against infectious agents. Alum stimulates clusters of proteins, called inflammasomes, that reside within certain immune cells. These inflammasomes then secrete proteins called cytokines, which activate and recruit more immune cells to strengthen the body’s response to the agent. The discovery of how alum activates the innate immune system promises to facilitate the design of new and improved vaccine adjuvants.
Read more about the scientists’ discovery of how alum works.
Other Vaccine Ingredients
Vaccines may also contain substances to prevent contamination during manufacturing, to maintain a vaccine’s potency at less-than-optimal temperatures, or to keep multi-dose vials of vaccine sterile after they are opened. One such ingredient is thimerosal, which since the 1930s has been added to some vaccines and other products because it is effective in killing bacteria and in preventing bacterial contamination.
One product of the degradation or metabolization of thimerosal is ethyl mercury, an organic derivative of mercury. The only known side effects of receiving low doses of thimerosal in vaccines have been minor reactions such as redness and swelling at the injection site.
For general information on thimerosal, read the following:
For information on NIAID-supported studies on thimerosal, read the following:
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