Vivaldi 2: coronavirus (COVID-19) new variant (B.1.1.7) in care homes study report
Published 7 May 2021
Applies to England
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Methodology
The Vivaldi study, led by University College London, was set up in June 2020 to investigate SARS-CoV-2 transmission, infection outcomes and immunity in residents and staff in care homes in England.
For this paper, researchers analysed 4,442 positive PCR samples (samples where SARS-CoV-2 was detected), collected from October to December 2020.
PCR tests for SARS-CoV-2 are designed to detect 3 parts of the virus:
- S gene
- N gene
- ORF1ab
The then new variant known as B.1.1.7 (or the Kent variant) has changes in its S gene, or spike gene, which mean the PCR tests did not detect this particular target.
This means researchers were able to identify the proportion of infections caused by the Kent variant by looking at the samples in which the other 2 targets, the N gene and ORF1b, were detected, but not the S gene.
Results
Among the samples under investigation, the proportion of infections caused by the B.1.1.7 variant rose from 12% in the week beginning 23 November 2020 to 60% just 2 weeks later, in the week beginning 7 December 2020.
One of the most significant findings of the study was that in the South East of England, the proportion increased from 55% to 80% over that period. In London, where the variant spread fastest, the proportion increased from 20% to 66%.
The researchers said the timing of infections suggested the B.1.1.7. variant may have been passed from staff to residents, with positive cases among older people occurring later.
Conclusion
The proportion of infections in care home staff and residents caused by the variant B.1.1.7 rose from 12% in the week beginning 23 November to 60% of positive cases just 2 weeks later, in the week beginning 7 December. With the B.1.1.7 variant spreading fastest in London during this period.
See the report Spread of a variant SARS-CoV-2 in long-term care facilities in England.