The Welsh Government’s COVID-19 Technical Advisory Group (TAG) wanted to understand the impact of re-opening schools on COVID-19 transmission between staff and children. Using data from the SAIL Databank, Dr Daniel Thompson, as part of the One Wales cross-institutional partnership, analysed household and school data to inform Government decisions.


As schools reopened across Wales following prolonged periods of school closures due to the COVID-19 pandemic, evidence was required to examine the role of the school setting in transmission between pupils and school staff.


The study by Dr Thompson and the One Wales cross-institutional partnership linked population data, anonymised at the individual, household and school level, to assess transmission of COVID-19 within the school setting.

The team used data held within the SAIL Databank to create an e-cohort of school children (ages 4-17), school staff, and linked household members for both children and staff, the sample size of tests studied and the numbers of infections were substantial. They assessed the likelihood of a positive test in pupils and staff in relation to other recent cases in linked pupils, staff or their households over the period from August to December 2020.

Impact and outcomes

Findings suggested that pupil to pupil COVID-19 transmission is likely, but the effect on the wider school population and staff can be minimised through the implementation of strict mitigation measures. In Wales, this has informed decision making around school openings following prolonged school closures during the national lockdown that began at the end of 2020.

Although the study was conducted in Wales, the findings can be generalised to the UK and many parts of the world in temperate climates where schools have around 30 pupils per class and are largely educated indoors. The study directly informed Welsh Government’s COVID-19 Technical Advisory Group (TAG) and the UK’s Scientific Advisory Group for Emergencies (SAGE), making it a great example of using health data to inform policy in a fast pace and ever-changing climate.

“This was the first population-level study of this kind and being able to link school, household, education and pathology data via the SAIL Databank was significant. This shows the real value of data providers who make anonymised data available for researchers, for the benefit of public health.”

The study was co-authored with Hoda Abbasizanjani.

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