A potential vaccine that would prevent the most deadly and aggressive type of breast cancer — triple-negative breast cancer — is undergoing testing.

The key protein for the vaccine, which would be a “holy grail” of cancer treatment, was found through “a matter of luck and tenacity in going through databases and looking for proteins,” Dr. Vincent Tuohy said, almost like finding a needle in a haystack.

The vaccine works by jumpstarting the immune system and attacking any tumors that contain a specific protein that should not be present unless a woman is lactating.

“Once we’ve established that we can produce an immune response, we want to rapidly move it earlier to the disease process again, to the prevention setting where we think it will have an even greater impact,” Dr. Thomas Budd said.

Tuohy and Budd are leading a trial still in its early stages. If successful, the vaccine would be given to young healthy women at higher risk for breast cancer, which is known as a triple-negative.

“It’s prophylactic, and it targets six different pathogens,” Tuohy said when asked how this vaccine differs from previously seen treatments. “We need a 21st-century vaccine program to develop the immune defenses and primary immune defenses against diseases we confront with age like breast cancer and ovarian cancer.”

These types of studies offer hope to women touched by cancer. “I was 35 years old,” Kristi Blair said when asked when she was diagnosed with cancer. “My youngest was three at the time.”

Blair was diagnosed with stage two breast cancer just four years after her own mother died from the disease. She hopes that her four daughters will benefit from advances in science, like the potential vaccine.

“I’m just really grateful and feel hopeful. It’s tangible hope,” said Blair, who participated in another trial at the University of Washington. “You are participating and advancing the research that does ultimately affect patients in the future and if not right now.”

The medical achievement — that was unimaginable 50 years ago — is now a possibility.