Health
A four-monthly jab may one day replace the need to regularly take pills.
The jab was tested on 72 patients with high blood pressure and it was found to work without serious side-effects.
The researchers and independent experts said the findings were promising but large-scale trials were now needed.
High blood pressure, which affects a quarter of all adults, doubles the risk of dying from heart disease or stroke and is blamed for 60,000 deaths a year in UK.
Immunisation may be of particular benefit to people who find it difficult to stick to high blood pressure medication
The researchers believe the vaccine, which works against the hormone angiotensin, which causes blood vessels to constrict and increase blood pressure, may offer a simple alternative.
They tested two different doses of the vaccine - 300 microgrammes and 100 microgrammes - as well as a dummy vaccine during the 14-week trial.
The jabs were given at the start, and after four weeks and 12 weeks - enough to give a patient four-month resistance.
Neither dose significantly lowered blood pressure at night.
But during the day the larger dose significantly lowered blood pressure, especially during the late morning peak when blood pressure is known to increase.
And, importantly, the vaccine did not have any serious side-effects with the worst being mild flu-like symptoms.