"We've seen a lot of treatments that have very early promise, but with follow-up studies just don't pan out, said Dr. Jay Brooks, chair of hematology and oncology at Ochsner Health System in New Orleans. "But it's interesting and something I would love to use in my practice if it proved successful."
The study is ongoing, and Mittendorf said it should finish in the fall of 2012. She hopes to launch a larger trial for the vaccine after that.
Scientists have been pursuing the idea of treating cancer with a vaccine, a method that would mean a more targeted, less toxic approach to treating the disease. Provenge, a vaccine for treating prostate cancer, was the first cancer vaccine approved by the U.S. Food and Drug Administration, getting the agency's nod in 2010. The development of other vaccines for melanoma and lung cancer are also under way.
Other vaccines for breast cancer have been attempted, and some have targeted the HER2 protein. But experts say the results in the current study are more encouraging than most.
"It is exciting to imagine that a vaccine could prevent recurrence of breast cancer," said Dr. Harold Burstein, a breast cancer specialist at Dana Farber Cancer Institute in Boston. "These are provocative data that will hopefully generate enthusiasm for a definitive, large trial to assess this vaccine."
Mittendorf said the vaccine isn't useful for treating patients with advanced forms of the disease and isn't intended to replace other forms of treatment but to work in conjunction with them to fight breast cancer.
"We've gotten pretty good at taking care of breast cancer, but even as good as we are now there are still patients who recur and succumb to disease," she said. "Any tools we can use to prevent that from happening we should use."
ABC News' Dr. Ruby Shandilya contributed to this report.