REACT-1 round 9 final report: Continued but slowing decline of prevalence of SARS-CoV-2 during national lockdown in England in February 2021
File(s)
Author(s)
Type
Working Paper
Abstract
Background
England will start to exit its third national lockdown in response to the COVID-19 pandemic
on 8th March 2021, with safe effective vaccines being rolled out rapidly against a
background of emerging transmissible and immunologically novel variants of SARS-CoV-2.
A subsequent increase in community prevalence of infection could delay further relaxation of
lockdown if vaccine uptake and efficacy are not sufficiently high to prevent increased
pressure on healthcare services.
Methods
The PCR self-swab arm of the REal-time Assessment of Community Transmission Study
(REACT-1) estimates community prevalence of SARS-CoV-2 infection in England based on
random cross-sections of the population ages five and over. Here, we present results from
the complete round 9 of REACT-1 comprising round 9a in which swabs were collected from
4th to 12th February 2021 and round 9b from 13th to 23rd February 2021. We also compare
the results of REACT-1 round 9 to round 8, in which swabs were collected mainly from 6th
January to 22nd January 2021.
Results
Out of 165,456 results for round 9 overall, 689 were positive. Overall weighted prevalence of
infection in the community in England was 0.49% (0.44%, 0.55%), representing a fall of over
one third from round 8. However the rate of decline of the epidemic has slowed from 15 (13,
17) days, estimated for the period from the end of round 8 to the start of round 9, to 31 days
estimated using data from round 9 alone (lower confidence limit 17 days). When comparing
round 9a to 9b there were apparent falls in four regions, no apparent change in one region
and apparent rises in four regions, including London where there was a suggestion of
sub-regional heterogeneity in growth and decline. Smoothed prevalence maps suggest large
contiguous areas of growth and decline that do not align with administrative regions.
Prevalence fell by 50% or more across all age groups in round 9 compared to round 8, with
prevalence (round 9) ranging from 0.21% in those aged 65 and over to 0.71% in those aged
13 to 17 years. Round 9 prevalence was highest among Pakistani participants at 2.1%
compared to white participants at 0.45% and Black participants at 0.83%. There were higher
adjusted odds of infection for healthcare and care home workers, for those working in public
transport and those working in education, school, nursery or childcare and lower adjusted
odds for those not required to work outside the home.
Conclusions
Community prevalence of swab-positivity has declined markedly between January and
February 2021 during lockdown in England, but remains high; the rate of decline has slowed
in the most recent period, with a suggestion of pockets of growth. Continued adherence to
social distancing and public health measures is required so that infection rates fall to much
lower levels. This will help to ensure that the benefits of the vaccination roll-out programme
in England are fully realised.
England will start to exit its third national lockdown in response to the COVID-19 pandemic
on 8th March 2021, with safe effective vaccines being rolled out rapidly against a
background of emerging transmissible and immunologically novel variants of SARS-CoV-2.
A subsequent increase in community prevalence of infection could delay further relaxation of
lockdown if vaccine uptake and efficacy are not sufficiently high to prevent increased
pressure on healthcare services.
Methods
The PCR self-swab arm of the REal-time Assessment of Community Transmission Study
(REACT-1) estimates community prevalence of SARS-CoV-2 infection in England based on
random cross-sections of the population ages five and over. Here, we present results from
the complete round 9 of REACT-1 comprising round 9a in which swabs were collected from
4th to 12th February 2021 and round 9b from 13th to 23rd February 2021. We also compare
the results of REACT-1 round 9 to round 8, in which swabs were collected mainly from 6th
January to 22nd January 2021.
Results
Out of 165,456 results for round 9 overall, 689 were positive. Overall weighted prevalence of
infection in the community in England was 0.49% (0.44%, 0.55%), representing a fall of over
one third from round 8. However the rate of decline of the epidemic has slowed from 15 (13,
17) days, estimated for the period from the end of round 8 to the start of round 9, to 31 days
estimated using data from round 9 alone (lower confidence limit 17 days). When comparing
round 9a to 9b there were apparent falls in four regions, no apparent change in one region
and apparent rises in four regions, including London where there was a suggestion of
sub-regional heterogeneity in growth and decline. Smoothed prevalence maps suggest large
contiguous areas of growth and decline that do not align with administrative regions.
Prevalence fell by 50% or more across all age groups in round 9 compared to round 8, with
prevalence (round 9) ranging from 0.21% in those aged 65 and over to 0.71% in those aged
13 to 17 years. Round 9 prevalence was highest among Pakistani participants at 2.1%
compared to white participants at 0.45% and Black participants at 0.83%. There were higher
adjusted odds of infection for healthcare and care home workers, for those working in public
transport and those working in education, school, nursery or childcare and lower adjusted
odds for those not required to work outside the home.
Conclusions
Community prevalence of swab-positivity has declined markedly between January and
February 2021 during lockdown in England, but remains high; the rate of decline has slowed
in the most recent period, with a suggestion of pockets of growth. Continued adherence to
social distancing and public health measures is required so that infection rates fall to much
lower levels. This will help to ensure that the benefits of the vaccination roll-out programme
in England are fully realised.
Date Issued
2021-03-04
Citation
2021
Copyright Statement
© 2021 The Author(s)
Publication Status
Published