What is herd immunity and has the UK reached it?

The term ‘herd immunity’ has been floating around since the Covid-19 pandemic began.

Sweden appeared to adopt a herd immunity strategy early on in the pandemic – as businesses, restaurants and schools remained open while other parts of Europe, and the world, locked down.

Now that the majority of the UK population has been vaccinated against the virus, virologist Dr David Matthews, a coronaviruses expert from the University of Bristol, told The Telegraph that he thinks the UK is getting close to reaching it.

He said: ‘In terms of herd immunity – by which we mean the virus has managed to reach everybody and therefore most people will have a level of immune memory – I suspect we’re very close to it.’

Here’s a reminder of what herd immunity is – and if the UK really is on track to reach it.

What is herd immunity?

In a piece for Metro.co.uk, junior doctor Samara Linton explained how herd immunity works.

Dr Linton says the term ‘describes the situation where a disease outbreak is unlikely to spread because sufficient people are vaccinated against the disease.’

‘This protects people who cannot have the vaccine, for example, for medical reasons. It is thought that 95% of vaccination coverage is needed for herd immunity.’

When it comes to coronavirus, herd immunity would mean that either:

• Enough people would catch the virus and have the antibodies to protect themselves against it
• Enough people would have the vaccine, and therefore those antibodies.

In December 2020, the World Health Organisation said that, in the case of coronavirus, herd immunity should be achieved through vaccination – not exposure to the deadly virus.

Even if it is reached one day, ‘herd immunity’ doesn’t mean that nobody will catch the virus again, or that it will go away completely.

We already know people who have had the virus can catch it again.

But it could mean that there are no more uncontrollable, lockdown-requiring outbreaks.

And when people are vaccinated, they are less likely to be hospitalised or die from the disease.

Has the UK reached herd immunity from coronavirus?

Not yet. And how close we are is up for debate.

Some experts say we are getting close, while others say we can’t possibly know.

According to the Office for National Statistics (ONS), almost 91% of UK adults would be positive for Covid antibodies.

That’s the average estimated number of people who would test positive for antibodies across the UK – meaning they have some protection from the virus.

As of June 28, the most recent data at the time of writing, England is at 91.9%, Wales at 92.6%, Scotland at 88.6% and Northern Ireland at 90%.

The most recent vaccine data also shows that 46 million people have had dose one, while 37 million have had two.

All this suggests that herd immunity is not a far-off possibility.

When speaking to The Telegraph, virologist Dr Matthews added: ‘Assuming nothing truly spectacularly left field happens, then this pandemic is pretty much over for the UK.

‘I suspect we will not see a major surge this winter, or any serious levels of fatalities.

‘The more we close the gap on the last 10% who haven’t had the vaccine, the better we will be. Everyone will eventually meet the virus and it is far better to do so vaccinated.’

Generally speaking, the more people who take up the first and second doses of the vaccine, the better.

But remember that the above ONS data on antibodies only includes adults – not children under the age of 18.

And, as the Mayo Clinic points out, there are a few major factors to consider with vaccines.

We don’t yet know how long efficacy of the vaccines will last (further study is needed).

They’re not all equally effective against all the current variants – plus what if a new variant appears in future?

Children aren’t routinely receiving the vaccine, either – which Kit Yates, a senior lecturer in mathematical sciences at the University of Bath, points out in a piece for the British Medical Journal.

‘Another important factor is heterogeneity of the population – understanding that not everyone mixes with everyone else equally. This is particularly important when we are vaccinating by age brackets,’ he wrote.

‘Immunity will not be spread evenly… if there are large demographics that are not immune then the disease can still spread freely in these groups.

‘By not offering the vaccine to children, for example, we are providing a large reservoir of unprotected people in whom the virus can freely circulate.’

Kit also added: ‘Conceptualising herd immunity as ‘all or nothing’ is not particularly helpful. Generally as immunity builds up in the population, it slows the spread.’

This idea, that the UK population is currently at different stages of vaccination, has been echoed in other expert comments.

An associated professor in biomedical technology, Dr Alexander Edwards, from Reading University, told i News in early July:

‘We have a mixture of natural infection, partial vs full vaccination (one or two doses), and different vaccines. All of these give different levels of protection. The consequence: it’s hard to predict when we’ll reach herd immunity.’

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