A vaccine to combat high blood pressure is being developed by scientists who believe that it could dramatically reduce the incidence of the condition that may affect as many as 40% of adults in Britain and increases the risk of both heart disease and strokes.
Trials of an injection to control a protein that causes blood vessels to narrow have been shown to be safe and provoke an immune response in both animals and humans, the Swiss company responsible told an American Heart Association conference in Dallas yesterday.
The immunisation of rats has so far suggested that their blood pressure could be lowered to a similar extent as that achieved by a routinely used drug, called an ACE inhibitor.
The first human trial involved just 16 people, but a second, involving 72, is under way in Germany, with results expected in the second half of next year. However, it will probably be several years before the vaccine has been thoroughly tested and is ready for the market, and the company is looking for partners to develop it further.
More than 600 million people worldwide suffer from hypertension. Experts have previously suggested about a third of those with high blood pressure in Britain are not even aware of it, while another third are not being treated with drugs but might benefit from them.
Even those who are on medication, usually a combination of pills, do not always take them as they should; sometimes because they feel well and the drugs have side effects such as a dry cough, skin rashes, allergies, tiredness or dizziness. However, not everyone with the condition needs medication: stopping smoking, reducing salt intake and getting more exercise may stop their pressure reaching danger levels.
Dr Martin Bachmann, the chief scientific officer of the Swiss company, Cytos Technology, said a vaccine could replace such drugs. "Between 50 and 80% of people do not take their drugs. If you only had to have a vaccine once every half year, and combined it with a check up with the doctor, it would make compliance that much better," he said.
"We have shown efficacy and safety in rats. We have shown safety in humans, we have also shown we can induce a response in humans." He said other companies had so far had "a hard time" in showing that a hypertension vaccine would work even in animals.
The vaccine works against a protein called angiotensin II. Dr Bachmann said that if blood pressure results in humans matched those already obtained in rats, the vaccine had the potential to have long-lasting effects.
But a British heart expert urged caution, saying suppressing angiotensin for months at a time could lead to other problems. Peter Weissberg, the medical director of the British Heart Foundation, said: "It looks to be a fairly novel approach, but whether it is one that will fly is another matter altogether. The biggest problem is it assumes a single cause of high blood pressure. If that were the case, it would be very easy.
"We have angiotensin for a reason. If one loses a lot of blood in a car crash, for instance, it kicks in to keep blood pressure up and compensate for that blood loss. With a normal drug that combated angiotensin, people faced with such a crisis could immediately be taken off them," he said.