The long-time dream of a vaccine to prevent breast cancer may be a step closer to reality, according to new research presented this week at the 29th Annual San Antonio Breast Cancer Symposium. Researchers presented the results of a vaccine
trial targeting HER2, a protein that is related to cell growth and is commonly overexpressed in breast cancer cells.
The researchers isolated and purified a piece of that protein, called E75, that is normally exposed on the surface of cancer cells. The purified protein, along with factors that stimulate the immune response is injected into patients monthly. All
vaccinated patients showed a rapid increase in immunologic response up until month 4, at which point the response plateaued. Months after the vaccination series, vaccinated patients had a 50 percent reduction in breast cancer recurrence
compared with similar breast cancer patients who were not vaccinated.
The vaccine had minimal side effects, generally limited to redness around the injection site. There were no serious systemic effects.
September 09, 2026 
