An experimental breast cancer vaccine proven to initiate a strong immune response that helps slow the growth of tumors is taking the next steps in its clinical trial phase.

The study, published in JAMA Oncology focused on a protein called human epidermal growth factor receptor 2 (HER2) which is found in around 30% of breast cancer cases and can be overproduced 100x in some patients.

Some people with an overgrowth of the protein can have a natural immune response called cytotoxic, or cell-killing, which has been shown to help stop it from recurring. The goal is to mimic this process with the vaccine, a news release on Nov. 3 explained.

There were 66 women with metastatic cancer who enrolled in the study. Phase one was intended to test the safety of the vaccine while phase two will be a larger, randomized clinical trial. Researchers are recruiting patients now.

"The results showed that the vaccine was very safe," lead author Dr. Mary "Nora" L. Disis, a UW professor of medicine, Division of Medical Oncology, and director of the Cancer Vaccine Institute said in the release.

"In fact, the most common side effects that we saw in about half the patients were very similar to what you see with COVID vaccines: redness and swelling at the injection site and maybe some fever, chills and flu-like symptoms,"

The Centers for Disease Control and Prevention said that every year in the U.S. there are about 264,000 cases of breast cancer diagnosed in women and about 2,400 in men.

There are about 42,000 women and 500 men in the U.S. who die each year from breast cancer.

"If the results of the new randomized-controlled phase II trial of the vaccine are positive, it will be a strong signal for us to rapidly move forward to a definitive phase III trial. I have high hopes that we're close to having a vaccine that can effectively treat patients with breast cancer," Disis said.

Breast cancer