A small clinical trial (conducted by the U.S. military) of an experimental vaccine designed to trigger the immune system to fight breast cancer suggests that it may reduce the risk of death for most patients.

Breast cancer represents about one quarter of all cancer cases and that makes it deadlier than other forms of the disease.

“We now have something we think works in the majority of women with breast cancer who are currently underserved. It’s also very, very well-tolerated, like a flu shot,” said George Peoples, chief of surgical oncology at Brooke Army Medical Center in San Antonio and director of the Cancer Vaccine Development Program at the U.S. Military Cancer Institute and senior author of the study, the Washington Post reported.

The vaccine (licensed by biotech firm, Apthera) is designed to treat women with tumors that generate a protein called HER-2. About one-fourth of breast cancer patients have the gene mutation that leads to excess HER2 proteins. In these cases, tumors tend to grow faster and are more likely to recur than tumors that do not carry the protein.

The new vaccine, called NeuVax, was tested in women whose tumors generated low levels of HER-2 as well as in women with high levels of the protein. The trial included 163 patients. After a 30 month-period, the injected vaccine was shown to cut the risk of death for all patients by half, and in the group of patients with low-expressing HER-2 tumors, no deaths were reported.

The trial also showed cancer recurred in 10.7 percent of vaccinated low-expressors, compared with 18.2 percent of the control group.

“This is a potential way to immunize patients to lower the risk of recurrence,” said Linda Benavides, a resident in general surgery at Brooke Army Medical Center at Fort Sam Houston in San Antonio, who was the study’s lead author.

She also added that a planned Phase III trial of NeuVax in more than 700 patients will test the vaccine solely in women with tumors that generate low levels of HER2, a group for which immune-targeting therapy is currently unavailable.

Women with high levels of HER-2 are currently treated with Herceptin, also known as trastuzumab, an expensive antibody-based drug made by Genentech Inc.

According to the American Cancer Society, about 182,000 women in the U.S. will be diagnosed with breast cancer this year.

The study was presented Sunday at a meeting of the American Association for Cancer Research in San Diego.