adjuvant

adjuvant \AJ-uh-vuhnt\, adjective:

1. Serving to help or assist; auxiliary.
2. Assisting in the prevention, amelioration, or cure of disease.

noun:
1. A person or thing that aids or helps.
2. Anything that aids in removing or preventing a disease, esp. a substance added to a prescription to aid the effect of the main ingredient.
3. Immunology. a substance admixed with an immunogen in order to elicit a more marked immune response.

Some people think the benefit of screening is huge, and others say that the reduction in death rates is due primarily to adjuvant therapy, Berry says. No one has known for sure, and although we still don't know for sure, this is the best set of analyses that is possible given the available information.
-- "Decline in Breast Cancer Deaths Explained by Use of Screening and Adjuvant Therapies", M. D. Anderson News Release, October 26, 2005

It's unlikely it will be needed this fall, especially if further tests show that one standard shot is good enough to protect people from the virus. But using adjuvant could prove helpful in future years, or if the flu took a turn for the worst, said Dr. Wilbur Chen, a vaccinologist at the University of Maryland's Center for Vaccine Development, who is leading the NIH-sponsored tests.
-- Kelly Brewington, "Stretching the supply of the swine flu vaccine", The Baltimore Sun, September 14, 2009

The new vaccine is made from a single CMV protein that was combined with an experimental adjuvant, a substance that's added to vaccines to boost their efficacy.
-- Serena Gordon, "Trial Vaccine May Protect Against Serious Viral Infection", U.S. News, March 18, 2009

Adjuvant comes from Latin adiuvāns, adiuvant-, present participle of adiuvāre, to help.