Independent report

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

Published 10 March 2022

Methodology

A representative cross-section of volunteers in England, aged 5 and over, tested themselves with swabs from 8 February 2022 to 1 March 2022 (inclusive). Swabs were analysed using polymerase chain reaction (PCR) for the presence of SARS-CoV-2.

Results

Over the 22 days of testing which form these round 18 findings of REACT-1, 2,731 samples tested positive from a total of 94,950 valid swab results, giving a weighted prevalence of 2.88% (2.76%, 3.00%) or 288 people per 10,000 infected. This compares to a weighted prevalence in the previous round, round 17 (5 January to 20 January), of 4.41% (4.25%, 4.56%), and is the second highest prevalence recorded in a round of REACT- 1.

In round 18 high weighted prevalence was observed at all ages ranging from 1.68% (1.41%, 2.01%) in those aged 75 years and over to 4.69% (4.01%, 5.48%) in those aged 5 to 11 years.

Weighted prevalence in those aged 5 to 11 years was higher than in all other age groups.

Weighted prevalence fell between round 17 and round 18 at all ages.

Between-round R was 0.96 (0.95, 0.97) in those aged 17 years and under, 0.96 (0.95, 0.96) in those aged 18 to 54 years, and 0.96 (0.96, 0.97) in those aged 55 years and weighted prevalence fell during round 18 in:

• those aged 5 to 17 years with a within-round R of 0.79 (0.74, 0.84)

• those aged 18 to 54 years with a within-round R of 0.92 (0.89, 0.96)

• trend in weighted prevalence among those aged 55 years and over suggested an increase in weighted prevalence with a within-round R of 1.04. (1.00,1.09)

At regional level, the highest weighted prevalence in round 18 was 3.33% (3.04%, 3.66%) in South East, up slightly from 3.23% (2.94%, 3.55%) in round 17.

The lowest weighted prevalence was observed in round 18 was in the North East at 2.33% (1.88%, 2.87%).

The highest weighted prevalence in round 18 final was observed in:

• large households including 6 or more people at 3.36% (2.76%, 4.09%), 5 people at 3.33% (2.87%, 3.85%), 4 people at 3.88% (3.58%, 4.20%) and 3 people at 3.06% (2.79%, 3.35%) – compared to 2.50% (2.33%, 2.68%) and 1.87% (1.65%, 2.11%) in 2-person and single-person households, respectively

• households with one or more children at 3.88% (3.63%, 4.14%) – compared to 2.31% (2.19%, 2.44%) in households without children

• those having been in contact with a confirmed COVID-19 case at 10.35% (9.72%, 11.02%) or a suspected COVID-19 case at 6.86% (5.77%, 8.15%) – compared to 1.73% (1.62%, 1.84%) for those without such contact

• those not shielding at 3.08% (2.93%, 3.23%) – compared to 2.39% (2.16%, 2.65%) in those reporting shielding

• those reporting classic COVID-19 symptoms (loss or change of sense of smell or taste, fever, new persistent cough) in the month prior to swabbing at 15.06% (14.21%, 15.95%) or other symptoms at 3.85% (3.52%, 4.22%) – compared to 1.17% (1.08%, 1.27%) in those without symptoms

Among those who tested positive and reported on symptoms, 28.6% reported no symptoms in round 18 compared to 23.5% in round 17.

Viral lineages were determined for 1,195 of 1,392 positive samples collected up to 21 February 2022. All but one was Omicron sub-lineages and one (0.1%) was a sub-lineage of Delta. Among the Omicron sub-lineages, there was a daily growth rate advantage for BA.2 compared to BA.1 or BA.1.1 corresponding to an estimated R additive advantage of 0.40 (0.36, 0.43).

Conclusion

During the 22 days covered by the period of this report, high levels of infection with SARS-CoV-2 were observed in England in February 2022. The prevalence of SARS-CoV-2 infections overall was 288 per 10,000 people infected.

The highest rates were observed regionally in the South East and nationally in those aged 5 to 11 years. Of all the positive samples sequenced in this round, 99.9% of those were Omicron variant, with one sub-lineage of Delta detected. Among the Omicron sub-lineages, a daily growth rate advantage for BA.2 compared to BA.1 or BA.1.1 was observed.