Imperial College London

1 in 16 infected with the coronavirus as REACT study records highest rates yet

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A lateral flow test

Coronavirus infections in England have climbed to a record level as the REACT programme reports the highest prevalence since it began in May 2020.

According to the study’s latest surveillance data, based on almost 110,000 swab tests taken between 8 and 31 March, around 1 in 16 tested positive during this period, or 6.37% of the population. This is more than double the study’s previous findings when 1 in 35 had the virus as of 1 March, or 2.88% of people, and 40% higher than the first Omicron peak in January.

The scientists from Imperial found that infections were doubling every 30 days with an estimated reproduction number (R) of 1.07.

"Although restrictions have ended, I would urge people to still behave cautiously to help protect others who might be vulnerable." Prof Paul Elliott School of Public Health

The vast majority of the analysed positive samples were the Omicron BA.2 ‘stealth variant’ (named due to the absence of certain genetic changes that can distinguish this variant easily from others). As of 22 March, the team estimated that 94.7% of the samples were BA.2, which is double the study’s previous estimated figure from 19 February (47.2%). In January, 0.8% were BA.2.

A very small number of recombinant Omicron variants were also detected (five XE and three XL), which are hybrids of the original BA.1 Omicron strain and BA.2. Because the number of these recombinants was so small, it’s not possible to tell from the data whether these variants are more transmissible than others.

Compared to previous data infections have risen in all age groups and remain highest in primary school-aged children, with almost 1 in 10 (8.81%) 5-11-year-olds testing positive. However the most recent trends show that the rate of new infections is likely slowing or falling in the younger age groups aged 5-54. This was not seen in older people above the age of 55 where infections were found to still be rising, having almost tripled to 4.61% in the oldest age group, aged 75+.

Booster vaccines were rolled out by the NHS in September last year, starting with older age groups. Younger people therefore received their third dose more recently than older people, which may partly explain these findings as research has shown that vaccine effectiveness against infection falls over time.

Professor Paul Elliott, director of the REACT programme from Imperial’s School of Public Health, said: “These trends are concerning since when a very high number of people are infected, this may lead to more people becoming seriously ill and needing to go to hospital.

“Although restrictions have ended, I would urge people to still behave cautiously to help protect others who might be vulnerable, and avoid contact with other people if you have symptoms. This will help to slow the spread of the virus and lessen its impact on the NHS and our lives more broadly as we enter this next phase of the epidemic.”

These findings from the REal-time Assessment of Community Transmission (REACT-1) programme, led by Imperial College London with Ipsos MORI and commissioned by the Department of Health and Social Care, are available here in a pre-print report and are being submitted for peer-review.

Impact of vaccination in school children

For this latest round of the REACT study, 109,181 people swabbed themselves at home and their samples were analysed by PCR testing. 6,902 of these were positive, giving an overall weighted prevalence of 6.37%. Weighting is where the researchers make adjustments to their calculations to ensure the sample reflects England’s population.
Infection prevalence rose to a high level in all regions of the country, with the highest in the South West (8.13%) and the lowest in the West Midlands (5.28%).

"I’d like to thank each and every REACT participant for contributing to what has been a vital study throughout the course of the pandemic." Dame Jenny Harries UK Health Security Agency

By age, infections have also increased in all age groups, with the smallest rise seen in secondary school-aged children, which rose from 3.42% to 4.71%. The prevalence in this age group, a high proportion of whom have been vaccinated, is half that of primary school-aged children, where far fewer have been vaccinated. This suggests that vaccination is helping to reduce the spread of the virus in secondary school-aged children.

Dame Jenny Harries, Chief Executive of the UK Health Security Agency (UKHSA), said: “These latest study results are another reminder that the pandemic is not over, and there is still a real risk to many of us catching COVID with infection rates so high. That is why it is sensible to wear a mask in crowded, enclosed spaces, keep indoor spaces ventilated and stay away from others if you have any symptoms of a respiratory illness, including COVID. 

“Vaccination continues to prevent a high number of cases resulting in severe disease, hospitalisation and death and remains the best way to protect us all. If you have not yet come forward for your primary or booster vaccine I would urge you to do so straight away – the NHS vaccine programme is there to help you and the sooner you are vaccinated the sooner you and your family and friends will be protected.” 

“I’d like to thank each and every REACT participant for contributing to what has been a vital study throughout the course of the pandemic in giving us insight into how COVID-19 has impacted the country.” 

Behaviours and risk factors

The study also looked at the rates of infections across different risk factors and behaviours. People who had been in contact with a confirmed COVID-19 case had a 1 in 5 chance of testing positive (17.84%). Of those who reported they had any of the ‘classic’ COVID-19 symptoms, almost 1 in 3 tested positive (27.57%).

"Vaccines remain our best defence." Sajid Javid Health and Social Care Secretary

There was very little difference in prevalence in people who said they always wear a face mask indoors (6.59%) compared to those who say they never wear one (5.48%). Those who were shielding also had a similar infection prevalence to those who were not (6.00%, 6.64%, respectively).

Health and Social Care Secretary Sajid Javid said: “Thanks to our plan to tackle Covid, we are leading the way in learning to live with the virus. We have made huge progress due to the success of our world-leading vaccination programme, access to antivirals for vulnerable people and increased scientific and public understanding about how to manage risk.

“Despite high infection rates, the population now has much stronger protection against Covid than at any other point in the pandemic.

“Vaccines remain our best defence and we are now offering spring boosters to the elderly, care home residents and the most vulnerable – so please come forward to protect yourself, your family, and your community, and continue to follow public health guidance if you test positive.”


Visit our website to download the preprint report

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Justine Alford

Justine Alford
Institute of Global Health Innovation

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Contact details

Tel: +44 (0)20 7594 1484
Email: j.alford@imperial.ac.uk

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