'Exponential Growth' in COVID Cases in England

Peter Russell

June 17, 2021

The number of people infected with the SARS-CoV-2 virus in England has increased rapidly, with most infections happening in children and young adults who had not received a vaccine, latest research found.

An analysis from The REal-time Assessment of Community Transmision-1 (REACT-1) study estimated that 0.15% of people had the virus, or around 1 in 670.

The data was based on 108,911 self-administered RT-PCR tests collected from participants from May 20 to June 7.

The research team, led by Imperial College London (ICL), reported that national prevalence of the virus had increased from 0.10%, or around 1 in 1000, since its previous survey in the second half of April to May 3.

R Number of 1.44

The scientists detected "exponential growth" between the two rounds with a doubling time of 11 days.

The R number was estimated at 1.44.

A rapid replacement of the Alpha (B.1.1.7) variant of SARS-CoV-2

with the Delta (B.1.617.2) variant was observed. "These data coincide with the Delta variant becoming dominant and show the importance of continuing to monitor infection rates and variants of concern in the community," said Prof Paul Elliott, director of the REACT programme.

The preprint study suggested that the link between infections, hospitalisations, and deaths had been weakening since February because of the vaccination programme. However, that trend had been reversing for hospitalisations since late April.

The highest prevalence of infections at 0.36% was seen in young people aged 18 to 24, followed by 0.35% for children aged 5 to 12.

Although prevalence in people under the age of 50 was 2.5 times that of those aged 50 and above, infections appeared to be growing at a similar rate in both groups, the scientists commented.

Steven Riley, professor of infectious disease dynamics at ICL, said: "Even though we are seeing the highest infection prevalence in younger people who are less susceptible to COVID-19, if this growth continues it will drive up infections in older, more vulnerable people, as the vaccines are not 100% effective and not everyone has been fully vaccinated.

"This would lead to more hospitalisations and deaths, and risks straining the NHS, which is why it's vital that people take up their vaccine offer and continue to stick to the rules."

Regional Variations

The researchers said the latest data showed substantial regional variations across England. The highest prevalence was found in the North West at 0.26%, up from 0.11% in the previous round, while the South West had the lowest at 0.05%, slightly down from 0.07%.

Commenting on the study for the Science Media Centre, Prof James Naismith, director of the Rosalind Franklin Institute, and University of Oxford, predicted "a further cycle of doubling further down the road", although the summer would "help blunt its growth".

Except for the Delta variant, "we would have been able to end restrictions with almost no risk as originally planned", he said.

"It must be understood that without vaccines, the Delta variant would have been a disaster for the UK," he added, leading to a shut down of society, "or health care collapse".

Matt Hancock, England's Health Secretary, said: "These findings highlight the stark context in which we took the difficult decision to delay step 4 of the roadmap out of lockdown."

Data published this week showed that the Pfizer/BioNTech vaccine was 96% effective, and the AstraZeneca/Oxford vaccine was 92% effective, against hospitalisation after two doses.

From Wednesday, people aged 21 and 22 in England have been eligible to book a COVID vaccine.


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