Background
Despite high levels of vaccination in the adult population, cases of COVID-19 have risen
exponentially in England since the start of May 2021 driven by the Delta variant. However,
with far fewer hospitalisations and deaths per case during the recent growth in cases
compared with 2020, it is intended that all remaining social distancing legislation in England
will be removed from 19 July 2021.
Methods
We report interim results from round 13 of the REal-time Assessment of Community
Transmission-1 (REACT-1) study in which a cross-sectional sample of the population of
England was asked to provide a throat and nose swab for RT-PCR and to answer a
questionnaire. Data collection for this report (round 13 interim) was from 24 June to 5 July
2021.
Results
In round 13 interim, we found 237 positives from 47,729 swabs giving a weighted prevalence
of 0.59% (0.51%, 0.68%) which was approximately four-fold higher compared with round 12
at 0.15% (0.12%, 0.18%). This resulted from continued exponential growth in prevalence
with an average doubling time of 15 (13, 17) days between round 12 and round 13.
However, during the recent period of round 13 interim only, we observed a shorter doubling
time of 6.1 (4.0, 12) days with a corresponding R number of 1.87 (1.40, 2.45). There were
substantial increases in all age groups under the age of 75 years, and especially at younger
ages, with the highest prevalence in 13 to 17 year olds at 1.33% (0.97%, 1.82%) and in 18 to
24 years olds at 1.40% (0.89%, 2.18%). Infections have increased in all regions with the
largest increase in London where prevalence increased more than eight-fold from 0.13%
(0.08%, 0.20%) in round 12 to 1.08% (0.79%, 1.47%) in round 13 interim. Overall,
prevalence was over 3 times higher in the unvaccinated compared with those reporting two
doses of vaccine in both round 12 and round 13 interim, although there was a similar
proportional increase in prevalence in vaccinated and unvaccinated individuals between the
two rounds.
Discussion
We are entering a critical period with a number of important competing processes: continued
vaccination rollout to the whole adult population in England, increased natural immunity
through infection, reduced social mixing of children during school holidays, increased
proportion of mixing occurring outdoors during summer, the intended full opening of
hospitality and entertainment and cessation of mandated social distancing and mask
wearing. Surveillance programmes are essential during this next phase of the epidemic to
provide clear evidence to the government and the public on the levels and trends in
prevalence of infections and their relationship to vaccine coverage, hospitalisations, deaths
and Long COVID.