A vaccine undergoing testing at the Mayo Clinic has reportedly removed cancer cells in a breast cancer patient, Fox news reports.

Florida resident Lee Mercker became the first patient to participate in a clinical trial for a new vaccine after being diagnosed in March with early-stages of the disease.

She told First Coast News she had “DCIS stage zero” breast cancer, meaning the cancer cells had not yet spread. She was left with three options -- have a lumpectomy where the cancer cells are removed, undergo a mastectomy where the breasts are removed, or join a clinical trial for a potentially life-saving vaccine to kill the cells and prevent them from coming back.

“I signed on the dotted line that day," Mercker said of the 12-week trial at the clinics Jacksonville campus.

“It’s supposed to stimulate a patient's own immune response so that the immune cells like t-cells would go in and attack the cancer,” said Dr. Saranya Chumsri, an oncologist at the world-renowned medical center.

Mercker said the process entailed a series of shots and tests.

“They always took your blood, you had a physical, they’d make your shot right there on the spot for you,” Mercker said. “It was three shots, all in a row, alternating arms, four shots, two weeks apart.”

“It’s supposed to be just off the shelf, kind of similar to when you get the flu shot or pneumonia shot,” Chumsri said.