Question to the Department of Health and Social Care:

To ask the Secretary of State for Health and Social Care, with reference to the ONS surveys of 30 October and 4 December 2020, whether he has made an assessment of (a) the reasons for the ONS downgrade of its estimate of covid-19 in England from 9.52 per 10,000 on 17 October to 4.89 per 10,000 on 17 October 2020 and (b) the effect of that revision on the Government’s decision to enter into a second national lockdown in November 2020; and what steps the Government is taking to ensure that future covid-19 data published by the ONS will not require significant revision at a later date.

The Office for National Statistics (ONS) have published an extensive methodology document in relation to their COVID-19 Infection Survey, which states that:

“All estimates presented in our bulletins are provisional results. As swabs are not necessarily analysed in date order by the laboratory, we have not yet received test results for all swabs taken on the dates included in this analysis. Estimates may therefore be revised as more test results are included”.

The ONS COVID-19 Infection Survey is one of the many data sources the Scientific Advisory Group for Emergencies include in their scientific advice to Government used to inform decisions on COVID-19 restrictions. Other data sources include the REACT STUDY, Test and Trace data and COVID-19 deaths and hospital admissions. Collectively this data highlighted the need to tighten restrictions in November 2020.

The ONS COVID-19 Infection Survey is a pilot study developed at pace to help monitor the situation as it evolves and is therefore undergoing continual quality improvement.