The surprising vaccine side effects that can improve long-term health

I am currently arranging to get a shingles vaccination. I had shingles at university and still bear the scars, so I really don’t want to risk getting it again. But I also have in mind the fact that the benefits of the shingles vaccine are not limited to preventing shingles. And this isn’t unusual. We’re discovering that many vaccines have benefits that go way beyond protecting against a single virus or bacterium – facts that are not nearly as widely known as they should be.

Let’s start with shingles. A study of more than a million people last year reported that those given the Zostavax shingles vaccine were 26 per cent less likely to die from heart disease or experience a stroke, heart attack or heart failure during an average of six years after the shot – a massive reduction in risk for such a simple, cheap and easy intervention.

What’s more, people given a newer shingles vaccine called Shingrix were 17 less likely to develop dementia in the next six years compared with those given Zostavax. Since several studies have shown that Zostavax also reduces the risk of dementia, the overall reduction in risk with Shingrix should be even larger. Several other vaccines, including those that protect against flu and tuberculosis, also appear to reduce the risk of dementia.

In the US and Australia, shingles vaccination is recommended for those over 50 or adults with weakened immune systems. Unless you fall into that last category in the UK, it’s only available through public healthcare to those aged 70 to 79. I don’t want to wait that long, so will have to go private.

Shingles is caused by the varicella zoster virus, which causes chickenpox when it first infects us in childhood and then lies dormant in nerve cells, causing shingles when reactivated. So it’s possible vaccinating children against chickenpox will have some benefits later in life, too, though I couldn’t find any studies looking at this.

Flu vaccines also have cardiovascular benefits. For instance, an analysis combining data from more than 9000 people involved in six trials found that those vaccinated against flu had a 34 per cent lower risk of a heart attack or stroke in the next year. The benefit was even greater for people with a recent history of heart problems.

The new vaccines for RSV, or respiratory syncytial virus, seem to help prevent heart problems, too. A study involving around 130,000 people over 60 found that those who had one kind of RSV vaccine were less likely to be hospitalised with heart or lung issues than those who went unvaccinated.

Then there’s the covid-19 mRNA vaccines. They turn out to boost the immune response to tumours in conjunction with immunotherapy, extending peoples’ lives.

I could keep listing examples, but let’s turn instead to why so many vaccines have these wider benefits. We don’t know the precise mechanisms for sure, but it’s not that surprising that they do.

Viruses can do lasting physical damage to the body, and the immune response to them can also harm tissues. So-called cytokine storms, in which the body overreacts and releases too many immune-stimulating signals, are often what kill people with infections such as flu or covid-19, for instance, and there’s growing evidence that multiple sclerosis is a result of the immune response to the Epstein-Barr virus.

Many viruses also target our immune system in various ways to help evade it, weakening our defences. HIV takes this strategy to the extreme, killing it off altogether.

There are also viruses that we can’t get rid of once they infect us, such as the varicella zoster virus. Some, such as human papillomavirus (HPV), even genetically modify our cells by inserting their genomes into ours – this is why HPV causes cancers.

The point is, even viral infections that we tend to regard as harmless, such as flu in young people, can have long-lasting effects that are not always obviously linked to those infections. Studies of long covid have helped raise awareness of this – and of the benefits of vaccines in reducing the risk of lingering harm.

There’s this idea in some circles that “natural immunity” from getting a disease is somehow better than vaccination. It’s bonkers for all the reasons above and more, and measles is a great example of why.

Measles vaccines have cut the number of deaths from the disease from more than 2 million a year before 1980 to under 100,000 in 2024. They have also had the unexpected effect of reducing the number of children dying from other infectious diseases.

Why? Part of the answer is that measles kills off some immune cells, leaving children more vulnerable to a wide range of infections for years afterwards. But measles vaccines also seem to train the immune system in a way that boosts its wider effectiveness. This training effect is so beneficial it’s even been suggested that we should keep giving children the measles vaccine even if measles is eliminated.

Of course, it would be too good to be true if all vaccines trained our immune systems in this way. There is evidence that a few vaccines have the opposite effect. But this doesn’t mean they don’t still save lives overall.

As ever with vaccines, the key question to ask is whether you are better off getting vaccinated than not getting vaccinated. To make an informed choice, you need to balance the risks of infection versus vaccination, taking into account the wider benefits of a vaccine too. All too often the focus is entirely on very rare or entirely imaginary adverse effects of vaccines.

I have no doubt what will make me better off. I’ll be getting my shingles vaccine, and a flu jab every year, and the RSV vaccine when it’s offered, at the very least.