After enduring record-breaking levels of Covid in the past six months, Britain has seen cases fall to their lowest for a year. But as the country eases back into a life more normal, will the disease remain in the background – or is another resurgence on its way?
Science editor Ian Sample explains how the virus is changing – and why one expert thinks infection rates “are not going to get down to very low numbers again in our lifetimes”.
Why have cases fallen so low?
Britain has weathered two major waves of coronavirus in the past six months, driven by versions of the highly transmissible Omicron variant. At the winter peak, official figures recorded hundreds of thousands of confirmed cases a day, although the true number of infections was substantially higher. The surge in infections bolstered immunity to Covid, particularly among the vaccinated, which in turn has helped to push cases down.
But there are other forces at work behind the dwindling numbers.
As with much older human coronaviruses that cause the common cold, cases of Covid rise and fall with the seasons, with more transmission in the winter and less in the summer months. We are now into a period where cases should naturally subside. Another important factor at play is the dramatic shift in testing habits.
Since April, most people have had to pay for Covid tests, meaning far fewer infections are being confirmed and logged as cases. Whereas lateral flow and PCR tests in the community once detected perhaps half of all Covid infections, they are now picking up less than one in 10, according to Paul Hunter, professor of medicine at the University of East Anglia. “The daily dashboard isn’t picking up anywhere near as many infections as it was,” he said.
According to the government’s Covid dashboard, daily cases in England have fallen by 98% since the start of the year. They now sit below 5,000 cases a day for the first time since last June.
In contrast, the Office for National Statistics, which estimates infection levels from swabs taken in random homes around the country, has recorded only a 73% fall in prevalence in England, from more than 3 million people infected in the week ending 31 December to nearly 875,000 in the week ending 21 May.
After the successive waves of infection and the UK’s mass vaccination programme, the proportion of people with antibodies against Covid is extremely high. In England, about 99% of over-25s have Covid antibodies, but levels are high even among pre-teens, with 89% or more of those aged 8 years and over carrying antibodies against the virus.
Will cases drop further over the summer?
They may fall a little more and remain low through the summer as people spend more time outdoors, but another rise before the autumn is not out of the question.
With the full relaxation of Covid rules, the steady filling of offices, and people gradually reverting to pre-pandemic behaviour, there is plenty of scope for the virus to spread. And as immunity wanes from vaccinations and past infections, protection against infection will be the first line of defence to fail.
Because protection against severe illness wanes more slowly, any rise in cases should not translate into high rates of hospitalisations and deaths unless another variant intervenes.
… but Covid maybe spreading differently
Over the past few weeks, scientists have noticed a shift in the Scottish data, with a higher proportion of lateral flow tests coming up positive in more affluent than deprived areas.
“It’s not clear if this is a long-term effect yet,” said Prof Rowland Kao, who studies infectious disease dynamics at the University of Edinburgh, “but if it holds it’s very unusual.”
The way Covid is circulating appears to have changed.
In summer 2020, daily cases fell to the low hundreds, but they may not get as low this summer, Hunter said. “It won’t continue falling for ever. Covid is undoubtedly becoming endemic. We are not going to get down to very low numbers again in our lifetimes.”
Despite huge uncertainties about the trajectory of the pandemic, the Joint Committee on Vaccination and Immunisation has proposed an autumn booster programme for people aged 65 and over, the clinically vulnerable, frontline health and social care workers and the staff and residents of care homes.
… And it is still evolving
Britain’s spring surge of Covid was driven by an Omicron variant called BA.2. Its dominance in the UK is now being challenged by two recent descendants, namely BA.4 and BA.5, which are driving a new wave of Covid in South Africa.
The UK Health Security Agency declared BA.4 and BA.5 “variants of concern” last week, as new data revealed they had a growth advantage over BA.2.
Another descendant causing concern is BA.2.12.1, which spreads faster still, and last week became the dominant variant in the US. So far, there is no evidence that any of them cause more severe disease, but as the original Omicron demonstrated in December, the danger comes from reaching more people. “Any increased spread without a decrease in severity could be a bad thing,” Kao said, adding that with plenty of virus in circulation around the world, we should expect more variants to come.