Coronavirus (COVID-19) Infection Survey, UK: 24 March 2023

The following points are for the week ending 13 March 2023 for England, Wales and Scotland, and the week ending 7 March 2023 for Northern Ireland.

• The estimated percentage of people testing positive for coronavirus (COVID-19) increased in England, and the trends were uncertain in Wales, Northern Ireland and Scotland.
• In England, the estimated number of people testing positive for COVID-19 was 1,493,200 (95% credible interval: 1,347,000 to 1,651,100), equating to 2.66% of the population, or around 1 in 40 people.
• In Wales, the estimated number of people testing positive for COVID-19 was 74,500 (95% credible interval: 48,200 to 108,100), equating to 2.41% of the population, or around 1 in 40 people.
• In Northern Ireland, the estimated number of people testing positive for COVID-19 was 26,000 (95% credible interval: 15,300 to 39,900), equating to 1.42% of the population, or around 1 in 70 people.
• In Scotland, the estimated number of people testing positive for COVID-19 was 136,200 (95% credible interval: 91,000 to 190,400), equating to 2.59% of the population, or around 1 in 40 people.
• In England, the estimated percentage of people testing positive for COVID-19 increased in the North West, the East Midlands and the South East, and the trends were uncertain in all other regions.
• In England, the estimated percentage of people testing positive for COVID-19 increased for those aged two years to school Year 11, and those aged 50 and over; the trends were uncertain for the remaining age groups.

There are higher levels of uncertainty in these latest estimates because of lower numbers of samples received. This higher level of uncertainty is shown by wider credible intervals. Details of potential bias in our latest estimates can be found in Section 4: Measuring the data.

For Northern Ireland, the reference week is the same as in our previous release, but estimates have been updated with additional test results received up to 7 March 2023. There were too few samples returned in Northern Ireland after 7 March 2023 to produce robust estimates.

Figure 1: The percentage of people testing positive for coronavirus (COVID-19) increased in England, and the trends were uncertain in Wales and Scotland in the week ending 13 March 2023

Estimated percentage of the population testing positive for COVID-19 on nose and throat swabs, England, Wales and Scotland, 6 March 2022 to 13 March 2023

Notes:

1. Modelled results are provisional and subject to revision.
2. These statistics refer to infections occurring in private households. The figures exclude infections reported in hospitals, care homes and/or other communal establishments.
3. Official reported estimates are plotted at a reference point believed to be most representative of the given week.
4. The official estimate presents the best estimate at that point in time. Modelled estimates are used to calculate the official reported estimate. The model smooths the series to understand the trend and is revised each week to incorporate new test results, providing the best indication of trend over time.
5. Official estimates are displayed over a rolling year up to the most recent week. The full time series of our official estimates from 27 April 2020 onwards are available in our Coronavirus (COVID-19) Infection Survey dataset.
6. There is a higher degree of uncertainty in our estimates for Wales and Scotland, compared with England. This is shown by wider credible intervals.
7. The reference week is 7 to 13 March 2023 for England, Wales and Scotland. The reference week for Northern Ireland is 1 to 7 March 2023, which is the same as in our previous publication. Therefore, we have not included charts for Northern Ireland in this figure, however updated estimates for Northern Ireland can be found in the accompanying dataset.

Download this chart

.xlsx

Age groups for children and young people

• "Aged 2 years to school Year 6" includes children in primary school and below.
• "School Year 7 to school Year 11" includes children in secondary school.
• "School Year 12 to those aged 24 years" includes young adults who may be in further or higher education.

Credible interval

A credible interval gives an indication of the uncertainty of an estimate from data analysis. The 95% credible intervals are calculated so that there is a 95% probability of the true value lying in the interval. A wider interval indicates more uncertainty in the estimate. Overlapping credible intervals indicate that there may not be a true difference between two estimates. For more information, see our methodology page on statistical uncertainty.

Reference dates

We aim to provide the estimates of positivity rate (the percentage of people who test positive) that are most timely and most representative of each week. In addition, to improve stability in our modelling while maintaining relative timeliness of our estimates, we report our official estimates based on the midpoint of the reference week.

This week, the reference week is 7 to 13 March 2023 for England, Wales and Scotland and the reference day is 10 March 2023. For Northern Ireland, the reference week is 1 to 7 March 2023 and the reference day is 4 March 2023. More information on reference weeks and days can be found in the Measuring the data section of our Coronavirus (COVID-19) Infection Survey, UK: 10 March 2023 bulletin.

Additional COVID-19 Infection Survey data

Our full Coronavirus (COVID-19) Infection Survey datasets for England, Wales, Northern Ireland, Scotland and our technical dataset are available. These datasets include our monthly incidence, sub-regional and single year of age analysis.

Potential bias

All participants are given a 14-day testing window, usually this means that samples returned could have been taken from participants during the first or second week. However, because the final testing window started on 28 February 2023, for the 7 to 13 March 2023 all samples were returned in the second week of the testing window. There is a possibility that some bias may have been introduced in who chose to return their samples in the second week, particularly as participants were informed that the survey was being paused. With the added flexibility of when respondents choose to test, participants may also be more likely to test when they experience symptoms.

Survey fieldwork

Survey fieldwork for the pilot study began in England on 26 April 2020. Fieldwork began on 29 June 2020 in Wales, 26 July 2020 in Northern Ireland, and 21 September 2020 in Scotland.

Remote data collection

The Office for National Statistics (ONS) Coronavirus (COVID-19) Infection Survey has moved from collecting data and samples through home visits by a study worker to a more flexible approach for participants. We introduced an online questionnaire and swab and blood samples are returned through the post (or by courier for some participants). Further information on what these changes mean and how the survey continues to be valuable can be found in our recent blog post: The COVID-19 Infection Survey is changing.

There were minimal differences between estimates of swab positivity produced from remote data collection methods, compared with data collected by study worker home visits. New data presented in our Coronavirus (COVID-19) Infection Survey, UK: 19 August 2022 bulletin were based on a combination of data collected remotely and by study worker home visits. New data presented from our Coronavirus (COVID-19) Infection Survey, UK: 26 August 2022 bulletin onwards were collected by remote data collection only. Further information on the effects of the change in data collection method can be found in our Coronavirus (COVID-19) Infection Survey quality report: August 2022 and our Coronavirus (COVID-19) Infection Survey quality report: December 2022.

Other Coronavirus Infection Survey (CIS) analysis and studies

This study provides the main measure of coronavirus infection in the UK. Other sources have provided data during previous stages of the coronavirus pandemic. For information on other studies see Section 4: Quality characteristics of the Coronavirus (COVID-19) Infection Survey (coherence and comparability) of the Coronavirus (COVID-19) Infection Survey: quality and methodology information (QMI), revised 20 January 2023.

Quality

More quality and methodology information on strengths, limitations, appropriate uses, and how the data were created is available in our Coronavirus (COVID-19) Infection Survey: methods and further information methodology and the Coronavirus (COVID-19) Infection Survey: quality and methodology information (QMI).