Professor Christl Donnelly

Prof Christl Donnelly


Professor of Applied Statistics (University of Oxford) Professor of Statistical Epidemiology (Imperial College London) Royal Statistical Society vice-president for external affairs

The REal-time Assessment of Community Transmission-1 (REACT-1) study has been tracking the spread of the SARS-CoV-2 virus in England approximately monthly since May 2020 as England’s first wave of infections declined. Over 2 million people have taken part to date. REACT-1 charted the complete replacement of Alpha by Delta from round 12 (21 May to 7 June 2021) to round 13 (24 June to 12 July 2021).

With round 16 (23 November to 14 December 2021) data REACT-1 documented Omicron’s early spread in England. Community-based surveillance studies can be critical in providing situational awareness and estimates of infection prevalence that are not biased by access to testing.

In February 2022, Natalie Dean wrote in her Nature article entitled Tracking COVID-19 infections: time for change:

“Shining examples of random sampling are the Coronavirus (COVID-19) Infection Survey run throughout the United Kingdom by the Office of National Statistics (ONS), and Imperial College London’s REACT-1 study.”

Tracking COVID-19 infections: time for change Such studies have provided crucial information to inform policymakers and stakeholders.


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