If there was a vaccine against heart attacks, would you take it?
In this edited extract from Vaccine Nation, Professor Raina MacIntyre poses a question everyone should ask themselves this flu season.
We are increasingly understanding the relationship between different infectious diseases and chronic diseases. In 2023, it was finally uncovered that the Epstein–Barr virus is a leading cause of multiple sclerosis (MS). Imagine a vaccine against MS, and a substantial reduction in the burden of MS after that vaccine is rolled out to populations. If you are affected by this debilitating disease or know someone who is, it will resonate that it may be preventable in the future. Human papillomavirus is the main cause of cervical cancer, and we are already seeing substantial declines in the rate of cervical cancer in countries that implemented vaccination of pre-teens. Hepatocellular carcinoma, a deadly form of liver cancer, is caused by the hepatitis B virus. Forty years after the introduction of hepatitis B vaccines, we are seeing a dramatic decline in liver cancer in countries that implemented universal infant vaccination. We will soon have mRNA vaccines that act directly against cancers. The leading cause of death and disease in the world, however, is cardiovascular disease. Heart attacks and strokes comprise the biggest burden of cardiovascular disease. If there were a vaccine against acute myocardial infarction, would you use it? After 10 years of working on the topic, this was the title of a paper I published in 2017.
There’s a well-documented relationship between respiratory viruses and cardiovascular disease. The largest body of evidence is around influenza, but studies also show that other viruses such as RSV and shingles, and the pneumococcus bacteria, can trigger heart attacks. For over 100 years, it’s been recognised that rates of death due to all causes peak in parallel to flu epidemics. About 20 years ago, a swag of studies showed a massive increase in the risk of heart attack in the weeks following a respiratory infection, especially influenza. The work of epidemiologists Professor Liam Smeeth and Professor Charlotte Warren-Gash from the London School of Hygiene and Tropical Medicine in the UK was particularly ground-breaking. They published a large body of work that showed the association of heart attacks and strokes with influenza, and several other infections, that set the scene for many others to follow. In a study led by Professor Smeeth, a heart attack or stroke was more likely to occur within one to three days after a respiratory tract infection, and influenza vaccination reduces this risk. Our own study, conducted in Sydney, found that almost 10 per cent of patients admitted with a heart attack had undiagnosed influenza, which may have triggered their heart attack, and that it may have remained undiagnosed had we not tested everyone on admission. One study using the US National Inpatient Sample with 22 million hospitalisations found that the influenza vaccine was protective against heart attack, stroke, cardiac arrest and death.
When I was a medical student in the 1980s, if you had a heart attack, your chance of survival to old age was greatly reduced. That is no longer the case because of amazing advances in rapidly restoring blood flow to blocked arteries. Advances in the medical treatment of coronary artery risk factors have also been substantial. The one aspect of heart attacks that has not changed much in terms of survival is a cardiac arrest. A cardiac arrest occurs when the heart goes into an abnormal rhythm, usually ventricular fibrillation, that does not allow the heart to pump blood as it normally does to the rest of the body. Survival from sudden cardiac arrest remains low. If you happen to have a cardiac arrest in hospital, where there is a resuscitation team and a defibrillator, your chance of survival is good. However, most people have their cardiac arrest in the community. When the heart is unable to pump blood to the brain and the body, it takes six minutes for brain death to occur. It’s estimated that about 20 per cent of the first presentation of a heart attack will be cardiac arrest. This is therefore the least preventable aspect of heart attacks, and it’s a very compelling reason to expand influenza vaccination to people in the age group where diagnosis of heart disease has not yet been made but who are at high risk. In our research, we showed that extending free influenza vaccines (currently available for people 65 years and over) to adults 50–64 years would achieve significant cost‑benefit for Australia by preventing the fraction of cardiac arrests associated with influenza.
Other vaccines can also reduce the risk of cardiovascular events, such as heart attack or stroke. Having shingles (herpes zoster) increases your risk of stroke and coronary artery disease, and vaccination is protective. I started researching shingles in the early 2000s while working at our National Centre for Immunisation Research and Surveillance. The first study I published, showing severe outcomes, including a 1 per cent rate of death after shingles. This was scoffed at by a disbelieving paediatrician colleague who said, ‘No one dies of shingles.’ Studies now show that having shingles can trigger a stroke or a heart attack, so it makes perfect sense that having shingles can kill you. Other serious complications of shingles include blindness if the virus reactivates around the eye, a condition called ophthalmic zoster. It can also cause meningitis, and I have personal experience of this. The most common serious complication of shingles is postherpetic neuralgia, a very painful condition that affects about 10 per cent of people with shingles and causes chronic pain after the rash has resolved. It’s a nasty, debilitating disease. Studies also show that the shingles vaccine protects against shingles, post-herpetic neuralgia and cardiovascular events, especially stroke. Despite being recommended and funded for older adults, the rate of vaccination is extremely low for this vaccine.
About 30 per cent of people in hospital with pneumococcal disease also suffer a major cardiovascular event, such as a heart attack or stroke. Pneumococcal disease is caused by the bacteria streptococcus pneumoniae (also known as pneumococcus) and is the leading cause of pneumonia worldwide. Pneumococcal vaccines reduce that risk, especially of heart attacks, and especially in people 65 years and over, across multiple different studies. Yet in Australia, we stripped away the recommendation for people aged 65 to 69 years. The kindest explanation I can think of is that they forgot to factor in the prevention of heart attacks into their cost-effectiveness analysis, although pneumonia prevention alone would have made it worth it. And in 2020, the year this recommendation came in, it would have been even more cost‑effective given pneumococcal disease was the most common bacterial complication of COVID-19. An alternative explanation is simply ageism – selectively slashing spending on older adults, despite having worked hard and paid their taxes all their lives.
RSV is another virus that has been found to increase the risk of heart attacks and strokes in older adults. It commonly causes outbreaks in aged care. In a nursing home study that I was involved in, RSV outbreaks were not as common as influenza, but they do occur and can have high mortality. In 2024, new RSV vaccines for adults 60 years and over became available – two have been approved in Australia – but are not provided free to eligible adults as yet. Like influenza, RSV causes severe disease in infants and the elderly. The infant RSV vaccine was approved for Australian infants in 2024, which is great news. The adult vaccines are too new for us to know if they reduce the risk of heart attacks and strokes, but on principle, they should.
Dr Ziyad Al-Aly, a clinician and scientist at the US Department of Veterans Affairs (DVA), was named in the TIME100 Most Influential People of 2023 for his seminal work on the long-term effects of COVID-19. Using data from the DVA, he published many high-impact studies showing that a single episode of COVID-19 can increase your risk of heart attacks, strokes, pulmonary emboli, other blood clots, new-onset diabetes and a range of other serious diseases, with the risk persisting for at least 12 months after the infection. Studies confirm that the virus can persist in the body long after the initial infection. This can lead to ongoing immunological and inflammatory effects. The COVID-19 vaccines show substantial protection against all these effects, including myocarditis and pericarditis. Although myocarditis and pericarditis can occur after vaccination in about 0.005 per cent of people, especially adolescent and young adult males, the risk after infection is much higher. We have been told that repeated exposure to COVID-19 will make it mild, but research shows the opposite – reinfection can be more severe and result in worse outcomes.
There is no doubt, however, that COVID-19 will contribute a major burden of chronic disease to the world. Cardiovascular disease is the leading cause of death and disability in the world and affects about 5 per cent of people. Long COVID will make this burden greater and will cause other kinds of chronic diseases that will substantially impact the health system. Sadly, policymaking bodies have not caught up with the science, and we find ourselves with restrictive policies for booster vaccines and antivirals, both of which may reduce this chronic burden of disease.
To find out about how vaccines can also help prevent dementia, what is going on with measles, and why we should be paying attention to the recent changes in bird flu patterns, read the rest of Vaccine Nation.
About the author: Raina MacIntyre is Professor of Global Biosecurity at UNSW and an NHMRC Research Fellow. She heads the Biosecurity Program at the Kirby Institute, UNSW. Her vaccine expertise is in older adults and immunosuppressed people.
