Experts, led by Wolfgang Lilleby at the Norwegian Radium Hospital started testing the vaccine in 2013.
The trial included 21 participants who were diagnosed with prostate cancer which had metastised – which means it had spread.
They were all also treated with hormone therapy and radiotherapy – standard procedure for many prostate cancer patients.
The first results of the study have now been published in a scientific journal.
This means their cancer had stopped spreading.
Experts revealed there had been reduction of a specific protein in the blood linked to the disease in 16 of the participants.
The tumour also was reported to have shrunk in ten patients.
However, tumours kept growing in five of the participants – who were given radiation therapy and hormone treatment.
Experts said they hope the vaccine can help delay any relapses in prostate cancer and help patients live longer.
The patients in the study were split into three groups and given different doses of the vaccine, but experts revealed a middle-range dose of the vaccine was the most effective.
Science Nordic reported that some of the participants in the study experienced some itchiness around the spot where the vaccine was given.
Some also had problems with dizziness, fatigue, diarrhoea and a more frequent need to urinate.
The researchers claim the vaccine is a more gentle form of treatment than other types of immunotherapy and chemotherapy.
“I doubt the vaccine is suitable for men with an advanced stage of cancer,” Dr Lilleby said.
“This is because it takes time to sensitise the immune system to cancer antigens, which help neutralise the body’s tolerance for cancer cells,” he said.