Bachmann adds that lowering early-morning blood pressure may reduce the risk of heart attack and stroke, which have been known to occur more frequently in the morning, as blood-pressure levels spike. A long-lasting vaccine that accomplishes this goal may offer more comprehensive relief, as opposed to pills taken on a daily basis.

"Due to the short half-life of these classical drugs, they don't work very well early in the morning, since people usually take their pills around breakfast," says Bachmann. "However, it is early in the morning when most heart attacks and strokes happen, and our trial demonstrated very good efficacy early in the morning."

Some scientists, however, raise concerns over a vaccine's long-lasting and potentially irreversible effects on blood pressure. For example, Michael Alderman, an expert in hypertension and the chairman of the department of epidemiology and social medicine at Albert Einstein College of Medicine, in the Bronx, NY, says that there are daily situations in which raising blood pressure is an advantage.

"If you're running down a football field or walking up a flight of stairs, blood pressure goes up to prevent you from fainting," says Alderman. "People who have taken antihypertensive medications have been known to faint, and the same risk exists with pills. But you're changing the equation if you're on a longer-term effect that you cannot reverse easily."

Additionally, it is unclear how the vaccine would affect the immune system as it stimulates antibodies continuously over a period of several months.

Bachmann says that after analyzing blood samples from volunteers after the trial, his group found no change in the amount of antibodies and other immune cells present, indicating that the vaccine had minimal effect on immune-system production.

Cytos plans to find a pharmaceutical partner in the next few months to collaborate on a larger trial of the vaccine, and together they will work on fine-tuning dosage to further lower blood pressure, particularly in people with mild to moderate forms of hypertension.

"We would expect the vaccine to be particularly useful in this patient population, since the vaccine alone may suffice to control blood pressure," says Bachmann. "In more severely hypertensive patients, this would most likely not be the case, since they usually need more than one type of drug."