1. General information about these data sources

Ethical scrutiny

ONS statisticians complete an ethical assessment of all proposed uses of a data source before work begins, and before they are given permission to access the data by the ONS Information Asset Owners (IAO). IAOs are senior ONS officials who are responsible for data sources, including protecting confidentiality and ensuring appropriate use.

For some new uses, notably where there may be more challenging ethical concerns, ONS statisticians will seek advice and ethical approval from the National Statistician’s Data Ethics Advisory Committee (NSDEC). Committee members have relevant expertise, provide scrutiny and challenge, and crucially, are independent.

Ethical scrutiny often involves exploring the balance between any data protection risks and the public good that could come from the new work. Most importantly, this scrutiny helps the ONS to ensure that we consider carefully whether we should produce a new statistic or not.

Minutes are published so the committee's views and approvals are transparent and available for the public to see. More information on the ethics self-assessment tool used by ONS researchers, and the NSDEC, can be found on the UK Statistics Authority's website.

Links to relevant NSDEC minutes are included for each dataset.

Data protection

Data Protection Impact Assessments (DPIAs) are completed for all uses of data where there are inherent risks for processing personal data, for example, when processing large volumes of personal data or when processing personal data of a sensitive nature. The DPIA ensures appropriate controls are in place to minimise risks and to provide assurance around the safety of the data.

Access to data held within the ONS Data Access Platform (DAP) is only granted to security-cleared ONS researchers on a case-by-case basis. This is done through a request process, which provides a business justification, authorised by the ONS IAO with advice from the Security and Information Management team.

Access is given via a “project space”, which includes only the data required to carry out the analysis that has been approved, and only to the users who require access to those data. Users are not permitted to access direct identifiers (such as name, address, date of birth, or sex) for the purposes of analysis. Access to identifiers is limited to a smaller number of staff who are specially trained and only for the purposes of data linkage. These staff are not involved in analysis or statistical production so there is a separation of duties between data linkers and data analysts.

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2. Census

The census is undertaken by the Office for National Statistics (ONS) every 10 years and gives us a comprehensive picture of all the people and households in England and Wales. It is unique in covering everyone at the same time and asking the same core questions of everyone.


The primary purpose of the census is to give an accurate and reliable estimate of the number of people in England and Wales, and to show where and how they usually live. Census outputs are used widely for national and local policy, for planning and for targeting resources, and to identify areas of unfairness and inequality. As well as a source of demographic information, the census includes relevant data pertaining to health through self-reporting on disability and general health.

Within health, purposes of processing census data include:

  • producing statistics on coronavirus (COVID-19) to guide pandemic response and decision making; this includes increasing the accuracy of COVID-19 infection and mortality models and assessing the impact of COVID-19 on wider health and social outcomes
  • beyond COVID-19, enabling more granular health statistics to be produced through linkage of the Census data with electronic health records; statistics that can be broken down by the rich sociodemographic characteristics captured by the Census
  • updating socio-demographic data of health datasets to improve quality
  • improving the representation of underrepresented groups in health analysis

Additional information about ethical scrutiny

Relevant National Statistician's Data Ethics Advisory Committee (NSDEC) minutes for uses of this dataset include:

Data minimisation

Extensive consultation has taken place to decide on the questions that are asked in the census. We need to create a balance between user needs and the amount of data collected while retaining high statistical quality. Details of the topics are set out in the Census (England and Wales) Order on the UK Government's legislation website. Only data specified within census legislation were collected.

It is possible that, during the census, duplicate responses are received for individuals. To ensure the principle of data minimisation, individual responses overwrite responses for the same individual provided on the household questionnaire.

Some personal data may be processed where recording is necessary for safeguarding individuals. In these instances, the minimum amount of personal data will be held to achieve the required purposes and will only be held for as long as necessary. All operational personal data will be held for as long as required to achieve the necessary purpose and will be held within the guidelines of our data retention policies.

The practice of data minimisation will be followed to ensure we are not processing personal data that are not required for the specific purpose for which they were obtained. For projects using census data, the data fields being used are reviewed, with the inclusion of each field requiring justification within the study protocol.

Examples of impact

Census data provide central and local government with the information required for them to plan and fund local services effectively to meet the anticipated needs of the population. Other users of census include:

  • businesses, to understand their market and customers
  • voluntary organisations, to understand the communities they work with
  • academics, to use in their social science research

From a heath-specific point of view, the 2011 Census and Census 2021 data have also been a crucial part of producing COVID-19 statistics, through the linkage of the census data with the mortality and health data sources listed in this register. This allows the mortality and morbidity outcomes of interest to be broken down by the rich socio-demographic information collected by the census. For example, ONS statistics on the differences in COVID-19 mortality rates across ethnic groups were the first to provide evidence on these differences to Government and their scientific advisors.

In future, Census data linked to mortality, health and other data will be used to produce more granular statistics on the health of the nation, beyond COVID-19. This includes the ONS’ unique position in being able to bring health and non-health data together and therefore produce insights on areas such as the impact of health on labour market participation.

Read more about How others use census data.

Further information

More information about the census is available.

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3. Coronavirus (COVID-19) Infection Survey (CIS)

This survey captures incidence of COVID-19 (SARS-CoV-2) infection and prevalence of immunity to COVID-19 (SARS-CoV-2) in the UK general population. This is assessed through repeated cross-sectional household surveys with additional serial sampling and longitudinal follow-up. It is delivered in partnership with University of Oxford, University of Manchester, Public Health England and Wellcome Trust.

Legal basis for sharing data

This survey is conducted under consent from participants. The data collected are controlled by the Office for National Statistics (ONS).


In April 2020, the Department of Health and Social Care (DHSC) commissioned the ONS, in response to the COVID-19 pandemic, to develop and deliver a longitudinal study of the population prevalence of COVID-19 infection in the community.

The COVID-19 Infection Survey (CIS) provides regular insights on COVID-19 infection, incidence, antibody prevalence and transmission to enable detailed and timely understanding of COVID-19 and its impact across the UK population including the relationship between employment and health conditions, treatments and service use.

The CIS is the largest regular survey of COVID-19 infections and antibodies, providing vital information to help the UK's response to the pandemic. This includes linkage of the data to other data sources such as COVID-19 Test and Trace, and vaccines data, to enable additional COVID-19 statistics to be produced that would not be possible using the survey data alone.

Additional information about ethical scrutiny

The relevant National Statistician's Data Ethics Advisory Committee (NSDEC) minutes for uses of this dataset are the NSDEC minutes for November 2020 to January 2021 and the NSDEC minutes for August 2023.

Data minimisation

All data fields collected were reviewed, and the purpose for inclusion has been outlined in the study protocol, published on the Nuffield Department of Medicine's website.

For processing email test results, data have been minimised as much as possible to ensure the emails are comprehensible to the participants while minimising the amount of personal data used.

Examples of impact

When the CIS programme was set up, there was an overwhelming need for trustworthy, independent, and timely statistics on COVID-19 that could be conducted at a national and devolved level.

The results of the CIS contributed to the Scientific Advisory Group for Emergencies (SAGE) estimates of the rate of transmission of the infection, often referred to as “R”, and continue to contribute to epidemic estimates produced by the UK Health Security Agency (UKHSA).

The survey also continues to provide important information about the socio-demographic characteristics of people and households who have contracted COVID-19. The outputs have substantially informed the UK's response to the COVID-19 pandemic, supporting policies, tactical response, and academic research, and influencing public behaviours.

Further information

More information about the Coronavirus (COVID-19) Infection Survey methodology is available.

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