Dec. 11, 2025, 6:00 PM ESTBy Kaitlin SullivanWhen Chase Johnson was 31, her dog began acting strange. He was anxious, wouldn’t leave her side and, one day, pushed his nose into the side of her breast. Johnson felt a hard lump. “I wasn’t someone who was good at doing self-exams, I don’t think I would have found it otherwise,” Johnson, now 36, of Cary, North Carolina, said. “I had no family history of breast cancer.”Johnson was diagnosed in February 2021 with triple-negative breast cancer, an aggressive type of the disease that tends to grow quickly and spread to other parts of the body. Breast cancer treatment is determined in part by whether certain proteins are present on the tumor cells, including estrogen receptors and progesterone receptors, as well as a protein called HER2. Treatments can target these three proteins. Breast cancers with neither receptor and which produce little to no HER2 are deemed triple-negative, making them more difficult to treat.Johnson underwent four months of intravenous chemotherapy and surgery to remove her tumor and lymph nodes. After that, she had another six months of oral chemo and 24 rounds of radiation. Her treatment was considered successful, and afterward she began looking for ways to prevent the cancer from coming back. About 40% of women with triple-negative breast cancer have a recurrence within the five years of treatment, and in about 30% of those women, the cancer recurs in the brain. It can also re-emerge in the lungs, liver and lymph nodes. In December 2022, Johnson enrolled in an early-stage clinical trial at the Cleveland Clinic that is testing a novel vaccine that researchers hope could stop triple-negative breast cancer recurrences and, in some women, stop the cancer from developing in the first place. Johnson joined Cleveland Clinic’s Phase 1 clinical trial studying a vaccine for triple-negative breast cancer.Courtesy of Chase Johnson“I am literally doing anything possible to make sure this doesn’t come back,” Johnson said. “For triple negative, the resources are so limited; if the traditional treatment methods don’t work, you’re just kind of out of luck.”The vaccine targets a protein called α-lactalbumin, which is present in about 70% of triple-negative breast cancers and found on the surface of tumor cells. If successful, the vaccine would teach the immune system to make T-cells that attack and destroy cells with the protein. The latest findings of the Phase 1 clinical trial, which included 35 women, were presented Thursday at the San Antonio Breast Cancer Symposium in Texas. The trial looked at whether the vaccine was safe and if it triggered an immune response in three groups of patients. (It did not look at how the vaccine affected outcomes.) The first group, which included Johnson, was women who had recovered from early stage triple-negative breast cancer and were tumor-free but at high risk for recurrence. The second was women who had undergone treatment for early-stage disease and had remaining tumor cells. The third group had not yet been diagnosed with breast cancer, but carried a genetic predisposition, such as the BRCA gene, that put them at high risk for triple-negative cancer.The researchers found that 74% of the women developed an immune response to the vaccine — though what that result means for reducing recurrence or preventing disease is still unknown. “Whether this immune response will translate into reducing the risk of recurrence or preventing breast cancer, we don’t know that yet,” said trial leader Dr. G. Thomas Budd, a breast cancer medical oncologist at Cleveland Clinic’s Cancer Institute. The vaccine also appeared to be safe: Women reported redness or a lump at the injection site, but no serious adverse events were seen.One concern was whether the vaccine would trigger an autoimmune response, where the immune system mistakenly attacks the body. Women naturally produce α-lactalbumin when lactating, which the vaccine could train the body to attack. Because of this, Budd said he doesn’t recommend that women who want to breastfeed enroll in the trial. The Phase 1 results, while promising, only represent an early step in determining whether the vaccine will prove successful.A Phase 2 trial is expected to begin late next year. That trial will be the first to look at whether the vaccine can reduce the risk of a triple-negative breast cancer recurrence. If that goes well, future trials will test prevention in patients with a genetic risk, Budd said. Justin Balko, co-leader of the Breast Cancer Research Program at Vanderbilt-Ingram Cancer Center, said the most promising use for the vaccine would be to prevent a first cancer occurrence or a recurrence, rather than target lingering cancer cells.That’s because over time, tumor cells can learn how to hide target proteins from the immune system, Balko said. New cancer cells are less likely to develop this ability, he added.Vaccine exploration for triple-negative breast cancer is a welcome task, said Dr. Larry Norton, founding medical director of the Evelyn H. Lauder Breast Center at the Memorial Sloan Kettering Cancer Center in New York. The most effective targeted breast cancer treatments need estrogen or HER2 receptors to be present in tumors. “Triple-negative doesn’t have either, so we are left only with chemotherapy,” Norton said. Even if the α-lactalbumin-targeting vaccine is not effective in a Phase 2 trial, Norton said scientists are getting better at identifying the abnormal molecules found on different tumor cells. Those abnormalities serve as targets for novel therapies. “There was a time when we would say HER2 is the worst type of breast cancer you can have, then along came HER2-targeting therapies and now all of the sudden one of the worst prognosis markers becomes one of the best,” Norton said. “This could be the story of triple-negative breast cancer if we find a target for it.”Kaitlin SullivanKaitlin Sullivan is a contributor for NBCNews.com who has worked with NBC News Investigations. She reports on health, science and the environment and is a graduate of the Craig Newmark Graduate School of Journalism at City University of New York.