Project summary
Investigate whether pneumococcal polysaccharide vaccine lowers risk of heart attack and stroke.
What is the issue for NSW?
Heart attacks and strokes are caused by the build-up of cholesterol (called a plaque) in the arteries of the heart or brain, a process named atherosclerosis, which leads to death of heart or brain tissue.
Animal studies have shown that vaccination against the Pneumococcus bacterium reduces the size and number of plaques. The mechanism appears to be that the cell wall of the bacterium contains a fat that looks like the bad cholesterol that builds up in the plaque. Vaccination triggers the production of antibodies towards this cell wall fat and these antibodies cross react with the bad cholesterol, attacking and basically “clearing away” the plaque.
What does the research aim to do and how?
The obvious question has been whether pneumococcal vaccination can do the same thing in humans. Observational human studies are promising, indicating that people who receive the pneumococcal vaccine have a lower risk of heart attack and stroke than those who do not. Unfortunately, these studies are not randomised and it is possible that these results are confounded.
The Australian Study for the Prevention through Immunisation of Cardiovascular Events (AUSPICE) is the first and only registered study worldwide to test this hypothesis in a randomised controlled clinical trial. Funded by NHMRC ($1.8 million) in 2013, it has recruited 4725 people across six centres nationally, with half receiving the pneumococcal vaccine and half receiving placebo.
It is one year into the six year follow-up needed to have sufficient power to detect a 17% reduction in heart attacks and strokes. While waiting for endpoints to develop over the next five years, we will investigate the potential mechanisms of a protective effect; this was not covered by the original grant. One thousand participants have given blood samples at baseline and one month after vaccination, and agreed to undergo measures of atherosclerosis at baseline and two and four years after vaccination. We anticipate that those who get and respond to the vaccine will show a reduction in plaque during follow-up.
If a vaccine can protect against heart attacks and strokes, it will be a major public health advance. The vaccine has a well-established safety profile but is underused. If this study is positive, coverage could be increased (currently less than a third of those eligible get the vaccine) and the target age could be reduced from 65 to 55 to cover more of the population at risk. This fits squarely with the NSW Health priority of “Keeping People Healthy”.