Not for the first time in the coronavirus pandemic, the UK finds itself in a unique position. Through a combination of history, biology, mathematics and politics, the country stands alone in pitting an advanced vaccination programme against a substantial wave of Covid driven almost entirely by the fast-spreading Delta variant.
Nowhere in the world is the race between vaccination and virus more keenly watched than here.
Other countries – and Israel stands out – have vaccinated more of their population. India has endured more Delta cases.
But much of North America, Europe and Asia are behind the UK with their vaccine programmes and are only now seeing Delta take hold.
The World Health Organization believes Delta will become dominant. The variant accounts for a fifth of new cases in the US and but expected to dominate within weeks. After a 10-week decline, cases are rising in Europe. In France, the government’s lead science adviser, Prof Jean-François Delfraissy, has warned of a fourth wave driven by the variant.
“The UK is in an absolutely unique position,” says Mark Woolhouse, professor of infectious disease epidemiology at the University of Edinburgh. “We have the biggest Delta outbreak in a well-vaccinated country. We are a petri dish for the world.”
There is plenty other countries can learn from what happens in the UK in the coming months. Most obvious is how the variant spreads in the population and what impact different vaccines, and different levels of vaccination, have on cases, hospitalisations and deaths.
Analysis by Public Health England has already shown the variant to be about 60% more transmissible than the Alpha, or Kent, variant and perhaps twice as likely to hospitalise people. Countries looking on will want to know who are the people needing hospital care, who needs mechanical ventilation, who dies, and in what numbers.
There is already some good news. While the Pfizer/BioNTech and Oxford/AstraZeneca vaccines aren’t quite as effective against Delta as they are against the Alpha variant, particularly after one dose, two shots reduce the risk of hospitalisation from Delta infections by 96% and 92% respectively. This is hugely welcome and gives countries a handle on what’s to come.
“People will undoubtedly look at the UK and learn as much as they can from our experience,” says Prof David Salisbury, former director of immunisation at the Department of Health and assistant fellow on the Global Health Programme at Chatham House.
“If the UK has a certain percentage of people double vaccinated and France has a third less, they might extrapolate to what that could mean for them. I’m sure that’s what public health people will be doing in many countries when they look at the UK data.”
Perhaps the most crucial question is this: can vaccination break the link between Delta variant infection and hospitalisation, or between infection and death?
The concept of breaking the link entirely makes more sense in epidemiology textbooks than in the real world.
While vaccines massively reduce the risk of death, they do not reduce it to zero, and they do far less to prevent infection. When a highly transmissible variant such as Delta is in circulation, it will still have a good chance of spreading widely and finding those people who are unvaccinated, or not-well protected from their shots.
How well it does this in the UK will alert other countries to how threatened their own vaccination programmes may be.
“The link cannot be entirely broken unless you have eradicated the virus,” says Salisbury. “If the virus is still in circulation, there have to be some consequences from it.”
All of which leads to the related question of what proportion of the population needs to be vaccinated to crush a national epidemic – and is this even achievable?
Israel originally pushed down on cases with aggressive vaccination, but cases have risen again with the arrival of the Delta variant.
For now, Israel is keen to watch and wait, to see if cases rise, but not severe illness. But while Israel relies largely on the Pfizer vaccine, the UK has bet on Oxford/AstraZeneca.
For that reason, other countries that are banking on the cheaper, more easily stored Oxford/AstraZeneca vaccine will be watching the UK . “If the UK avoids serious damage it will be important for those countries that have been relying on Oxford/AstraZeneca,” says William Hanage, a professor of the evolution and epidemiology of infectious disease at Harvard.
To crush an epidemic of Delta variant, scientists believe 85% of the population need to be protected by a vaccine that prevents all onward transmission.
But that assumes the virus is allowed to let rip with no other measures to control it. “At the moment we clearly haven’t vaccinated enough people to stop the virus circulating,” says Woolhouse.
“What that tells you is we are not at the herd immunity threshold yet. The delta variant, being more transmissible, has raised the bar.”
Countries looking on will want to see how the UK handles this dilemma. Vaccination and the immunity people have from past infection will get us a long way, but more measures are likely to be needed to eventually control the epidemic.
Siân Griffiths, emeritus professor at the Chinese University of Hong Kong and the co-chair of the Hong Kong government’s inquiry into Sars, says south-east Asian countries are watching the UK, along with Israel, to see how they cope with Delta.
Many of these countries went for a zero-Covid approach and have extremely low vaccination rates. They are now seeing cases of Delta variant spring up and will need to throw more into vaccination. “What you’re seeing is a gradual realisation that it isn’t going to be a world without Covid,” she says.
As the UK goes into the autumn, a combined Covid and flu vaccination programme may swing into action, giving time for Australia, New Zealand and other countries in the southern hemisphere to see the impact before their winter arrives.
But there are behavioural lessons to be had too. While the UK has worrying inequalities around who takes up the vaccine, coverage across the population is the envy of the world.
“Many countries are trying out different ways to get people to come forward,” says Griffiths. “They might want to look at why the UK has come forward for vaccination in the numbers it has.”