Independent report

REACT-1 study of coronavirus transmission: January 2022 final results

Updated 7 March 2022

Methodology

A representative cross-section of volunteers in England, aged 5 and over, tested themselves with swabs from 5 January to 20 January 2022 (inclusive). Swabs were analysed using polymerase chain reaction (PCR) for the presence of SARS-CoV-2.

Results

Over the 16 days of testing which form these round 17 findings of REACT-1, 4,011 samples tested positive from a total of 100,607 valid swab results, giving a weighted prevalence of 4.41% (4.25%, 4.56%) or 441 people per 10,000 infected. This compares to a weighted prevalence in the previous round, round 16 (23 November to 14 December), of 1.40% (1.31%, 1.50%), and is the highest prevalence ever recorded in a round of REACT.

In round 17 the prevalence of for SARS-CoV-2 infections was higher in younger age groups.

Highest weighted prevalence by age was observed in those aged 5 to 11 years at 7.81% (7.04%, 8.64%) in round 17 near final, up from 4.74% (4.15%, 5.40%) in round 16.

From ages 12 to 17 years and 35 to 44 years, weighted prevalence ranged from 4.96% (4.11%, 5.98%) in those aged 18 to 24 years to 5.17% (4.52%, 5.90%). In those aged 12 to 17 years, more than doubling from what was observed in round 16.

Between round 16 and round 17 near final, weighted prevalence increased seven-fold from 0.48% (0.39%, 0.59%) to 3.06% (2.82%, 3.33%) in those aged 65 to 74 years and almost 12-fold from 0.21% (0.13%, 0.32%) to 2.43% (2.13%, 2.77%) in those aged 75 years and over.

At regional level, the highest weighted prevalence in round 17 was 6.85% (5.98%, 7.84%) in North East, up from 1.00% (0.70%, 1.42%) in round 16. The lowest weighted prevalence was observed in round 17 was in the South West at 2.93% (2.59%, 3.31%).

The highest weighted prevalence in round 17 near final was observed in:

• those living in urban areas at 4.72% (4.54%, 4.91%) compared to 3.15% (2.89%, 3.43%) for those living in rural areas
• those from Asian at 6.59% (5.76%, 7.53%), Black at 6.65% (5.41%, 8.14%), and Other at 7.10% (5.33%, 9.39%) ethnicities compared to White ethnicity at 4.13% (3.97%, 4.28%)
• large households including 6 or more persons at 7.51% (6.27%, 8.97%), 5 persons at 6.24% (5.53%, 7.03%), 4 persons at 5.38% (5.01%, 5.78%), or 3 persons at 5.01% (4.63%, 5.42%) compared to 3.39% (3.19%, 3.60%) in two-person households and 3.18% (2.88%, 3.51%) in single-person households
• households with one or more children at 5.91% (5.59%, 6.24%) compared to 3.58% (3.42%, 3.76%) in households without children
• those having been in contact with a confirmed COVID-19 case at 12.86% (12.22%, 13.52%) or a suspected COVID-19 case at 9.45% (8.19%, 10.87%) compared to 2.40% (2.26%, 2.54%) for those without such contact
• those who reported confirmed previous COVID-19 infection at 14.06% (13.46%, 14.69%) or with suspected previous COVID-19 infection at 3.84% (3.32%, 4.43%) compared to 1.75% (1.63%, 1.88%) in those who reported no previous COVID-19 infection
• those reporting not shielding at 4.61% (4.42%, 4.81%) compared to 3.43% (3.16%, 4.05%) in those reporting shielding
• those reporting classic COVID-19 symptoms 5 in the month prior to swabbing at 15.86% (15.07%, 16.70%) or other symptoms at 5.83% (5.43%, 6.27%) compared to 1.87% (1.74%, 2.01%) in those without symptoms
• among those who tested positive and reported their symptom status, 28.2% reported no symptoms in round 17 near final compared to 29.5% in round 16

Lineages were determined for 1,406 positive samples collected up to 20 January 2022. A total of 1,392 (99%) Omicron variants were detected; all other lineages were the Delta variant (1%) or a sub-lineage of Delta.

Conclusion

During the 16 days covered by the period of this report, we observed unprecedented levels of infection with SARS-CoV-2 in England in January 2022 and the almost complete replacement of Delta by Omicron. The prevalence of SARS-CoV-2 infections overall was 441 per 10,000 people infected.

The highest rates were observed regionally in the North East and nationally in those aged 5 to 11 years. Of all the positive samples sequenced in this round, 99% of those were Omicron variant; all other lineages were the Delta variant or a sub-lineage of Delta.