Roll up your sleeve: hypertension vaccine passes early test.

A new vaccine lowers blood pressure in hypertensive people, a study shows. The finding breaks ground in a field dominated by drug therapy.

Surges in blood pressure make physical exertion possible, but chronically elevated pressure spells trouble. Scientists have entertained the idea of immunizing people against high blood pressure for decades, but it hasn't been easy. The only other vaccine to reach the testing stage in people failed to reduce blood pressure.

A vaccine may augment or offer an alternative to blood pressure medications, known to cause side effects.

Several compounds orchestrate blood pressure changes, including a small protein called angiotensin. When cleaved by an enzyme, angiotensin signals blood vessels to constrict, increasing pressure.

Researchers created the new vaccine by binding angiotensin to a harmless fragment of a virus. The protein "is then recognized by the immune system as a virus," says study coauthor Martin Bachmann, an immunologist at Cytos Biotechnology in Schlieren, Switzerland. The immune system makes antibodies against angiotensin and pulls it out of circulation.

Bachmann and his colleagues gave 48 people with mild-to-moderate high blood pressure three injections of the vaccine over 12 weeks. Some received higher doses than others. Another 24 volunteers received sham injections. All patients used devices that monitored their blood pressure regularly day and night.

Two weeks after the last shot, those getting a higher dose of vaccine averaged systolic (top number) blood pressure that was 9 points less than those getting the placebo shots, the researchers report in the March 8 Lancet. The diastolic (bottom number) reading dropped only 4 points, a difference that could reflect chance.

However, compared with the sham-injection group, participants getting the higher vaccine dose had reductions of 25 points for the systolic reading and 13 points for the diastolic during early morning, when their risk of stroke is highest.

The antibodies circulate in the body for 17 weeks, less time than most vaccines.

The biggest problem doctors face in treating hypertension is patients' failure to take their pills, says Sheila Gardiner, a cardiovascular physiologist at the University of Nottingham, England. The vaccine approach might offer convenience, she says. "It's definitely better than taking pills day after day."

And though the blood pressure decrease may seem small, Gardiner says, even 5 points in the diastolic reading decreases the risk of heart failure and stroke by one-third.

It remains unclear whether the vaccine could engender a reaction against one's own tissues, says Ola Samuelsson, a nephrologist at Sahlgrenska University Hospital in Goteborg, Sweden. He expects pharmaceutical companies to conduct long-term tests that might answer that question.

The vaccine doesn't appear to be 100 percent effective, he says, and that's just as well. Some angiotensin in circulation would allow blood pressure to crank up in case of trauma.