The prevalence of coronavirus cases in England dropped by around 60% from February to March, with recent data suggesting the decline is “levelling off”, researchers have said.
Experts found that the rate of infection fell in all age groups and regions across those two months, with figures also indicating that the vaccine rollout could be “breaking the link” between infections, deaths and hospital admissions.
According to the latest round of the Real-Time Assessment of Community Transmission (React-1) study, one in 500 people on average was still carrying the virus in March.
Researchers found there have been “big falls” in prevalence of the virus in the South East and London from February to March, but there remain “persistent areas of higher prevalence” of the virus in the southern part of Yorkshire, and parts of the East Midlands and the North West.
To date, more than 1.5 million people have provided swabs to the React-1 study so experts can assess infection rates across the country.
The 10th round of tests was conducted between March 11 and March 30, with 140,844 swabs collected, returning 227 positive results.
This is compared with 689 positive results out of 165,456 swabs from February 4 to February 23.
The researchers’ findings, due to be released as a pre-print, were outlined in a briefing to journalists on Wednesday.
– The rate of infection in the community was 0.20% in March – down from 0.49% in February and 1.57% in January.
– While on average there had been an overall decline in Covid prevalence over the whole of February and March, researchers observed last month’s data indicated this had flattened off.
– Using March data alone, the reproduction number (R) – the average number of people an infected person is likely to pass the disease on to – was estimated to be 1.
– Covid-19 prevalence decreased across all age groups between February and March, with the highest prevalence now among five to 12-year-olds and lowest in those aged 65 and above.
– In February and March, the number of foreign journeys compared with earlier months was “very, very low” on average.
– Comparing infections and death and hospital admissions, researchers observed “fewer deaths per infection” than they would have expected based on recent prior months of the study.
Steven Riley, professor of infectious disease dynamics at Imperial College London, said: “The good news is prevalence has decreased by approximately 60% from the previous round in February to the current results now in March.
“The most recent data doesn’t show a continued obvious decline, we have a levelling off of prevalence, and that’s reflected in an R estimate of 1.
“And we see some divergence between our observed patterns of infection and patterns of death since January, which we think probably suggests that the mass vaccination is breaking that link to some degree between infections and deaths.”
Commenting on infection, deaths and hospital admissions data, he said: “We’re observing fewer deaths per infection than we would have expected based on the recent prior months of the study.”
He added: “To a lesser extent, we’re seeing fewer hospitalisations per infection as well.
“We think that this is a signal of how the vaccination programme is breaking the link, the previously strong link, between the pattern of infections and the patterns of deaths and hospitalisations.”
Prof Riley warned that if the vaccine rollout slowed down, then researchers would expect to see higher levels of infection.
Professor Paul Elliott, director of the programme at Imperial from the School of Public Health, said: “I think we’re beginning to see in our data the effect of the vaccine, certainly in severe outcomes.”
He added that more work was needed to look at the impact of the vaccine on prevalence and transmission.
Prof Elliott acknowledged that the “big decline” in the rate of infection had “flattened off” in March but said it was “good news” that it did not rise with the recent relaxation of restrictions, such as more permitted social mixing and the return of pupils to schools.
He said a “close watching brief” was needed as lockdown is eased further, with a “careful balancing act” needed.
Health Secretary Matt Hancock said: “These findings are promising and illustrate the significant impact that lockdown, combined with our phenomenal vaccination programme, is having on the prevalence of this dreadful virus.
“We are meeting our four tests for easing the lockdown and there are many reasons to be optimistic for the future, but we cannot let this come at the expense of vigilance today.
“The only way to safeguard the progress we have made as a country is by continuing to show caution and by doing everything we can to drive this virus into retreat – practising hands, face, space and meeting outdoors, and accepting the offer of a vaccine when it comes.”