Question to the Department of Health and Social Care:

To ask the Secretary of State for Health and Social Care, what methodology and data his Department uses to calculate the R reproduction rates of covid-19 transmission for local authority areas of England.

Individual modelling groups use a range of data to estimate growth rates and ‘R’ values, including:

- epidemiological data such as testing data, hospital admissions, intensive care unit admissions and deaths;

- contact pattern surveys that gather information on behaviour; and

- household infection surveys where swabs are performed on individuals.

Different modelling groups use different data sources to estimate these values using mathematical models that simulate the spread of infections. Some may even use all these sources of information to adjust their models to better reflect the real-world situation. Estimates can vary between different models, so evidence from several models is considered, discussed, combined and the growth rate and ‘R’ is then presented as ranges.

Rounding and differences between the data streams used in these individual model outputs that are combined account for differences between estimates of ‘R’ and estimated growth rates. The Scientific Advisory Group for Emergencies calculates ‘R’ at United Kingdom, devolved administration and at NHS England regional levels. It does not produce estimates for local authority areas.