Around one billion people in the world suffer from hypertension. Having a high blood pressure increases the risk for numerous diseases, like stroke and heart problems. Therefore, it is important to treat this condition immediately. 
Luckily, numerous drugs for the treatment of hypertension are widely available. Beta-blockers, ACE-inhibitors, calcium-antagonists, and diuretics are commonly used pharmaceuticals against hypertension. Currently, researchers are seeking better ways to deal with this condition.
Scientists from the University of Osaka, Japan, may have come up with a new treatment. This involves targeting the angiotensin II protein. Angiotensin II plays a major role in blood pressure physiology. It increases the blood pressure in a couple of ways. One is by stimulating the kidney to reabsorb more sodium (which increases the blood volume and therefore the blood pressure) via aldosterone. Another is by its direct action on the constriction of vascular smooth muscle. Moreover, the increased ADH production caused by angiotensin II leads to water retention.
Developing a vaccine that targets angiotensin II to decrease blood pressure in rats was no easy feat. This is because in healthy individuals (and animals), the activation of an immune response against proteins from our own body is inhibited. This made it difficult to accomplish the results.
Also, it was important to make sure that a too vigorous response from the immune system was avoided, as this could lead to dangerous side effects. This is why the researchers used DNA vaccine technology to make the vaccine. A part of the hepatitis B virus DNA was taken and merged with the DNA that codes for the angiotensin II protein.
The DNA was then placed in a so-called vector plasmid, allowing the angiotensin II-Hepatitis B DNA to be inserted into cells. Those cells then started to produce the fusion protein. This led to an immune response, which eventually resulted in the production of antibodies against angiotensin II and subsequently reducing the blood pressure in rats injected with the vaccine. 
Though a lot of work still needs to be done, these amazing results mark the beginning of developing a vaccine against hypertension for humans.
References: http://ish-world.com/downloads/pdf/global_brief_hypertension.pdf  Koriyama H, Nakagami H, Nakagami F, Osako MK, Kyutoku M, Shimamura M, et al., Long-Term Reduction of High Blood Pressure by Angiotensin II DNA Vaccine in Spontaneously Hypertensive Rats. Hypertension. 2015;66:167-174