A woman pleaded guilty to healthcare fraud charges after she gave fake flu vaccine to long-term care residents and then billed Medicare for it.

Martha Denise Gonzales could face up to 10 years in prison and fines totaling $250,000 when sentenced on Dec. 11, according to the U.S. Attorney for the Southern District of Texas.

Gonzales admitted to posing as a licensed nurse and administering vaccine to residents of a senior citizen living center who were at a health fair. She then electronically billed Medicare for the flu shots using the name and identification number of the doctor she worked for as a billing clerk. She also gave the fraudulent vaccine to nearly 1,100 employees and contractors of ExxonMobil in Baytown, TX.

The fluid contained in the syringes was purified water, not influenza vaccine. Gonzales’ co-defendant, Iyad Abu El Hawa, owner of Comfort & Caring Home Health and America Home Health Care Services, also pleaded guilty to healthcare fraud and misbranding of a drug.