Vaccination against a pressure-raising hormone safely lowered blood pressure in rats for up to six months, in early tests presented at the American Heart Association’s Scientific Sessions 2013.

The new DNA vaccine targets angiotensin II, a hormone that increases blood pressure by causing blood vessels to constrict. Medications that block the action of angiotensin II are widely used to control blood pressure, but must be taken daily to be effective.

In the study, blood pressure was reduced for up to six months in animals receiving the vaccine, and tissue damage associated with high blood pressure to the heart and blood vessels was reduced.

The vaccine didn’t cause any dangerous autoimmune reactions and there were no signs of damage to the kidney, heart or liver in the treated animals.

Researchers said they hope their Ang II DNA vaccine may one day offer a new treatment option for patients with high blood pressure.