Early study of blood pressure vaccine shows promising results
Publication Date:07/03/2008
People with high blood pressure might be able to have only three or four injections a year instead of taking tablets every day, after trials of a new vaccine showed promising results. But we need bigger, longer studies to find out more. It will be several years before a vaccine could be available.
What do we know already?
Many people get high blood pressure as they get older. High blood pressure can put you at risk of having a stroke or a heart attack.
Treatments for high blood pressure include a healthy diet, exercise and (for some people) medicines that you take every day. These treatments work well. But they can be difficult to stick to. Some people get side effects, or don't like the idea of taking tablets every day.
Blood pressure is controlled by hormones made by your body, including a hormone called angiotensin II. It makes your blood vessels narrower, which puts your blood pressure up. Some drugs used to control blood pressure stop the body from making angiotensin II, or stop it working.
Researchers are now testing a vaccine made of angiotensin II combined with a virus that's been made safe. They want to see if this will make the immune system see angiotensin II as an enemy, and produce chemicals (antibodies) to block it from working. Doctors think people might be more likely to have a vaccine a few times a year than remember to take daily tablets.
The researchers need to find out two things. Firstly, is the vaccine safe and does it cause side effects? Secondly, what effect does it have on blood pressure?
What does the new study say?
No one who took part in the study got long-term side effects from the vaccine. The most common side effects were soreness, redness and swelling where the injection went in. Some people felt mild flu-like symptoms. These side effects are common for many vaccines.
Researchers tested two doses of the vaccine. At the end of the study, people who had the higher dose had an average drop in blood pressure of about nine points more than people who had a dummy injection (placebo). This is about the amount you would expect if you took a low dose of blood pressure medicine. The lower-dose vaccine had no effect.
Other studies show that reducing blood pressure by about five points may reduce your chances of dying from a stroke or from heart disease. But this probably depends on how high your blood pressure is to start with.
Tell me more about the study's findings
The people in the study had injections of angiotensin II at the start of the study, again after 4 weeks, then again after 12 weeks. The researchers measured whether the immune system produced antibodies to block the effects of angiotensin II, throughout the study. This showed that the effects of the second injection lasted for about 3 weeks, and the third injection lasted about 17 weeks. Also, the effect built up over the course of the 3 injections.
So it might be possible to give people only a few injections a year. But we don't know how safe it is to block the effects of angiotensin II long-term. In some situations, such as if someone becomes very dehydrated, the body needs angiotensin II to keep the blood pressure up. If you're taking tablets, it's easy to reverse the effects by not taking them. But if you've had an injection that lasts 4 months, you can't reverse the effects easily.
The vaccine had a big effect on early morning blood pressure. Most people get a big increase in blood pressure between about 5 a.m. and 8 a.m. That may be why a lot of strokes happen at this time of the day. People who'd taken the high-dose vaccine had a much smaller increase in blood pressure early in the morning.
Where does the study come from?
The study was carried out by researchers in several hospitals in Switzerland and Germany, and by researchers working for the company developing the vaccine, Cytos Biotechnology. It was published in the medical journal The Lancet, which is owned by a company called Elsevier.
How reliable are the findings?
This is a good-quality study, but it was small and short-term. When scientists test a new drug or vaccine, they have to do a series of studies, starting with very small ones on healthy people, to make sure the drug doesn't cause very bad side effects.
Later, they do bigger studies to see if the drug is safe and works for people with the condition they want to treat. This vaccine study is called a 'phase 2' study. It included 72 patients, who had mild to moderate high blood pressure, but were otherwise healthy. The company making the vaccine now needs to do 'phase 3' studies, including hundreds of people with higher blood pressure and other health problems.
We also need research to show whether the vaccine actually prevents people from having heart attacks and strokes. There's no point having a vaccine that reduces blood pressure unless it also reduces the main risks of high blood pressure. This type of study takes several years to do.
What does this mean for me?
If you have high blood pressure, a vaccine is an exciting idea, but it's still a long way off. We need much more research to be sure that it's safe in the long term and that it cuts the chances of heart attacks or strokes. Medicine safety authorities will then need to weigh up the risks and benefits of the vaccine.
What should I do now?
If you're worried about your blood pressure, ask your GP surgery for a blood pressure check.
For people with high blood pressure, it's important to take your medicines and lead a healthy lifestyle to keep it under control. If you're having problems with your blood pressure medicine, see your doctor. Different drugs have different side effects, and you may find one that suits you better.
From:
Tissot AC, Maurer P, Nussberger J, et al. Effect of immunisation against angiotensin II with CYT006-AngQb on ambulatory blood pressure: a double-blind, randomised, placebo-controlled phase IIa study. The Lancet. 2008; 371: 821-27.
To find out more, see our information on high blood pressure.
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© BMJ Publishing Group Limited ("BMJ Group") 2007. All rights reserved
This information does not replace medical advice. If you are concerned you might have a medical problem please ask your Boots pharmacy team in your local Boots store, or see your doctor.
