An experimental breast cancer vaccine has been showing progress in slowing down the development of disease in patients.

Out of 14 women with advanced breast cancer who received the drug, half showed no sign of tumor growth a year after treatment, the Daily Express reported.

The vaccine had an effect even in those with immune systems weakened by the disease and chemotherapy.

The vaccine primes the immune system to target mammaglobin-A, a protein found almost exclusively in breast tissue. Breast cancer tumors produce it at abnormally high levels.

The scientists stated that the vaccine would not be effective in cancer patients with tumors that do not generate mammaglobin-A.

The research is published in the journal Clinical Cancer Research.