THURSDAY, March 6 (HealthDay News) -- A vaccine that blocks so-called angiotensin II receptors, thus relaxing blood vessels to lower blood pressure, may one day replace current blood pressure medications, a new study suggests.

The advantage of the vaccine is that it would only need to be given two or three times a year and should help patients adhere to their medication regimen, researchers say.

"We found the vaccine was well-tolerated, and it did lower blood pressure in hypertensive people," said vaccine inventor Martin Bachmann, of Cytos Biotechnology in Schlieren, Switzerland.

Currently, there are two problems with high blood pressure drugs, Bachmann said. "On the one hand, people just don't take them, and, on other hand, the drugs don't work very well early in the morning," he said.

In the United States, only about one-third of people with high blood pressure (also known as hypertension) have their blood pressure under control, according to background information for the study. Many people don't take their blood pressure medications because of side effects, concerns about the long-term effects of the drugs, and their lack of perceptible symptoms, Bachmann noted.

"Our vaccine would only have to be taken maybe twice or three times a year, not every day. In addition, it works best early in the morning," Bachmann said.

In the new study, Bachmann's team presented the results of an early trial of 72 patients with mild to moderate high blood pressure who were randomly assigned to receive the vaccine at two different doses or a placebo.

The patients' blood pressure was measured before the trial and 14 weeks after the trial began. The outcome the researchers were looking for was whether the vaccine was safe and well-tolerated.

Bachmann's team found that patients who received the higher dose of vaccine had a drop in their systolic blood pressure of 9 mm Hg and a 4 mm Hg drop in their diastolic blood pressure. The blood pressure drop was particularly significant in the early morning, where patients showed a 25 mm Hg drop in systolic blood pressure and a 13 mm Hg drop in diastolic blood pressure, compared with patients receiving a placebo.

Overall, the vaccine was well tolerated, with only 10 patients reporting flu-like symptoms after the injection. Such reactions are common with several vaccines, the researchers noted. In addition, some patients experienced mild irritation at the injection site.

The study results are published in the March 8 issue of The Lancet.

More extensive testing is needed before the vaccine could be made available to the public, Bachmann said. "We are moving on to eventually large trials," he said.

One expert thinks this finding could be a breakthrough in helping patients control their blood pressure.

"Poorly controlled blood pressure remains a worldwide health-care problem and contributes greatly to heart attacks, strokes, and cardiovascular deaths," said Dr. Gregg C. Fonarow, a professor of cardiology at the University of California, Los Angeles.

Although there are lifestyle modifications and a number of effective and reasonably well-tolerated medications that can help control blood pressure, many patients don't adhere to their regimens in a way that works effectively, Fonarow said. "A vaccinate for controlling blood pressure, if proven to be safe and effective, could represent an important therapeutic advance," he said.

This study is the first to show promising data with a vaccine against angiotensin II, a potent constrictor of blood vessels, in patients with mild to moderate hypertension, Fonarow said.

"While further studies for safety and efficacy, including ones that are larger and follow patients longer, are clearly necessary, this is an exciting development in the search for new and more effective means to help patients achieve and maintain control of high blood pressure," he said.

More information

To learn more about high blood pressure, visit the American Heart Association.

SOURCES: Martin Bachmann, Ph.D., Cytos Biotechnology, Schlieren, Switzerland; Gregg C. Fonarow, M.D., professor, cardiology, University of California, Los Angeles; March 8, 2008, The Lancet

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