Coronavirus (COVID-19) Infection Survey, UK: 24 December 2020

• In the most recent week, the percentage of people testing positive for the coronavirus (COVID-19) in England has continued to increase; during the most recent week (12 to 18 December 2020), we estimate 645,800 people (95% credible interval: 610,100 to 683,100) within the community population in England had the coronavirus (COVID-19), equating to around 1 in 85 people (95% credible interval: 1 in 90 to 1 in 80).

• Over the most recent week, the percentage of people testing positive has continued to increase sharply in London, the East of England, and the South East; London now has the highest percentage of people testing positive.

• In the most recent week, the percentage of people testing positive has increased for all age groups except those aged 50 to 69 years where there are early signs of an increase, and those aged 70 years and above in whom there are early signs of a decrease.

• The percentage of those testing positive has increased sharply in recent weeks in Wales; during the most recent week (12 to 18 December 2020), we estimate that 52,200 people in Wales had COVID-19 (95% credible interval: 40,800 to 65,300), equating to around 1 in 60 people (95% credible interval: 1 in 75 to 1 in 45).

• The percentage testing positive in Northern Ireland has increased in the most recent week; during the most recent week (12 to 18 December 2020), we estimate that 10,100 people in Northern Ireland had COVID-19 (95% credible interval: 6,100 to 14,900), equating to around 1 in 180 people (95% credible interval: 1 in 300 to 1 in 125).

• The percentage testing positive in Scotland has decreased in the most recent week; during the most recent week (12 to 18 December 2020), we estimate that 37,100 people in Scotland had COVID-19 (95% credible interval: 28,900 to 46,300), equating to around 1 in 140 people (95% credible interval: 1 in 180 to 1 in 115).

• In the most recent possible time period (14 to 18 December), London, the South East, and the East of England have the highest percentages of positive cases that are compatible with the new variant of the virus.

During the most recent week of the study, we estimate that 645,800 people in England had the coronavirus (COVID-19) (95% credible interval: 610,100 to 683,100)¹. This equates to 1.18% (95% credible interval: 1.12% to 1.25%) of the population in England or around 1 in 85 people (95% credible interval: 1 in 90 to 1 in 80). The ratios presented are rounded to the nearest 5. This is based on statistical modelling of the trend in rates of positive nose and throat swab results.

The estimates for non-overlapping 14-day periods (which underpin our modelled official estimates) are presented in Figure 3. The percentage testing positive in the latest 14-day period (5 to 18 December 2020) was 1.25% (95% confidence interval: 1.19% to 1.32%).

Figure 1: In the most recent week, the percentage of people testing positive in England has continued to increase

Official estimates of the percentage of the population in England testing positive for the coronavirus (COVID-19) on nose and throat swabs from 3 May 2020

Notes:

1. All estimates are subject to uncertainty, given that a sample is only part of the wider population. The model used to provide these estimates is a Bayesian model: these provide 95% credible intervals. A credible interval gives an indication of the uncertainty of an estimate from data analysis. 95% credible intervals are calculated so that there is a 95% probability of the true value lying in the interval.

2. Official reported estimates are plotted at a reference point believed to be most representative of the given week. Details of which day was used for each week can be found in the dataset that accompanies this bulletin.

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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.

Figure 2: In the most recent week, the percentage of people testing positive in England has continued to increase

Estimated percentage of the population in England testing positive for the coronavirus (COVID-19) on nose and throat swabs based on modelled estimates from 7 November 2020

Notes:

1. These results are provisional and subject to revision.

2. All estimates are subject to uncertainty, given that a sample is only part of the wider population. The model used to provide these estimates is a Bayesian model: these provide 95% credible intervals. A credible interval gives an indication of the uncertainty of an estimate from data analysis. 95% credible intervals are calculated so that there is a 95% probability of the true value lying in the interval.

3. Official reported estimates are plotted at a reference point believed to be most representative of the given week. Details of which day was used for each week can be found in the dataset that accompanies this bulletin.

4. Modelled estimates include all swab results that are available at the time the official estimates are produced. Additional swab tests that become available after this are included in subsequent models, meaning that modelled estimates can change slightly as additional data are included.

5. Official estimates should be used to understand the positivity rate for a single point in time. This estimate, based on the modelled estimate for the latest week, is our best and most stable estimate and is used in all previous outputs. The modelled estimate can be used to understand the recent trend. The modelling includes a set period of data and smooths the estimate over time.

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.xlsx

Notes for: Number of people in England who had COVID-19

1. This is based on model estimates from the reference point of the most recent week (12 to 18 December 2020), Wednesday 15 December 2020.

During the most recent week of the study (12 to 18 December), the percentage of people testing positive has continued to increase sharply in London, the East of England, and the South East. London now has the highest percentage of people testing positive.

In the most recent week, the percentage testing positive in the South West has increased. The percentages of people testing positive in the North West and Yorkshire and The Humber have continued to decrease in the most recent week.

The percentages testing positive have decreased in the most recent week in the North East and the East Midlands. Caution should be taken in over-interpreting any small movements in the latest trend.

Figure 4: Over the most recent week, the percentage of people testing positive has continued to increase sharply in London, the East of England, and the South East

Estimated percentage of the population testing positive for the coronavirus (COVID-19) on nose and throat swabs, daily, by region since 7 November 2020, England

Notes:

1. All results are provisional and subject to revision.

2. These statistics refer to infections reported in the community, by which we mean private households. These figures exclude infections reported in hospitals, care homes and/or other institutional settings.

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.xlsx

Estimates for non-overlapping 14-day periods (which underpin our modelled estimates) for regions in England are available in our dataset, and are provided for context.

In the most recent week (12 to 18 December), the percentages testing positive have increased for all age groups except those aged 50 to 69 years where there are early signs of an increase, and those aged 70 years and above in whom there are early signs of a decrease. Secondary school-age children continue to have the highest percentage testing positive. Caution should be taken in over-interpreting small movements in the narrower age groups, which have wider credible intervals.

In the data used to produce these estimates, the number of people sampled in the different age groups who tested positive for COVID-19 is lower relative to England overall. This means there is a higher degree of uncertainty in estimates for individual age groups over this period, as indicated by larger credible intervals.

Figure 5: In the most recent week, the percentage testing positive has continued to increase in primary and secondary school-age children and in young adults

Estimated percentage of the population testing positive for the coronavirus (COVID-19) on nose and throat swabs, daily, by age group since 7 November 2020, England

Notes:

1. All results are provisional and subject to revision.

2. These statistics refer to infections reported in the community, by which we mean private households. These figures exclude infections reported in hospitals, care homes and/or other institutional settings.

3. The modelled estimates are presented at the reference value for a region which is the East Midlands. This does not affect the overall trend over time, but estimated probabilities for other regions would vary in level.

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During the most recent week of the study¹, we estimate that 52,200 people in Wales had the coronavirus (COVID-19) (95% credible interval: 40,800 to 65,300). This equates to 1.72% (95% credible interval: 1.34% to 2.15%) of the population in Wales or around 1 in 60 people (95% credible interval: 1 in 75 to 1 in 45). The ratios are rounded to the nearest 5. Our modelling suggests that the percentage of those testing positive has increased sharply in recent weeks in Wales. This is based on exploratory modelling of throat and nose swab results.

We have presented the weighted fortnightly estimates in Figure 7. These data underpin the modelling. The percentage of people testing positive in the latest 14-day period (5 December to 18 December 2020) was 1.60% (confidence interval: 1.21% to 2.06%).

Figure 6: The percentage of those testing positive has increased sharply over recent weeks in Wales

Estimated percentage of the population in Wales testing positive for the coronavirus (COVID-19) on nose and throat swabs since 7 November 2020

Notes:

1. These results are provisional and subject to revision.

2. All estimates are subject to uncertainty, given that a sample is only part of the wider population. The model used to provide these estimates is a Bayesian model: these provide 95% credible intervals. A credible interval gives an indication of the uncertainty of an estimate from data analysis. 95% credible intervals are calculated so that there is a 95% probability of the true value lying in the interval.

3. Official reported estimates are plotted at a reference point believed to be most representative of the given week. Details of which day was used for each week can be found in the dataset that accompanies this bulletin.

4. Modelled estimates include all swab results that are available at the time the official estimates are produced. Additional swab tests that become available after this are included in subsequent models, meaning that modelled estimates can change slightly as additional data are included.

5. Official estimates should be used to understand the positivity rate for a single point in time. This estimate, based on the modelled estimate for the latest week, is our best and most stable estimate and is used in all previous outputs. The modelled estimate can be used to understand the recent trend. The modelling includes a set period of data and smooths the estimate over time.

Download the data

.xlsx

The Welsh Government also publishes results from this survey that describe COVID-19 infections in Wales in English and in Welsh.

Notes for: Number of people in Wales who had COVID-19

1. This is based on model estimates from the reference point of the most recent week (12 to 18 December 2020), Wednesday 15 December 2020.

During the most recent week of the study¹, we estimate that 10,100 people in Northern Ireland had the coronavirus (COVID-19) (95% credible interval: 6,100 to 14,900). This equates to 0.55% (95% credible interval: 0.33% to 0.81%) of the population in Northern Ireland or around 1 in 180 people (95% credible interval: 1 in 300 to 1 in 125). The ratios in this bulletin are rounded to the nearest 5. Our modelling suggests that in the most recent week, the percentage of people testing positive in Northern Ireland has increased. This is based on exploratory modelling of throat and nose swab results.

We have presented the weighted fortnightly estimates in Figure 9. These data underpin the modelling. The percentage of people testing positive in the latest 14-day period (5 December to 18 December 2020) was 0.61% (confidence interval: 0.38% to 0.92%).

Figure 8: In the most recent week, the percentage of people testing positive in Northern Ireland has increased

Estimated percentage of the population in Northern Ireland testing positive for the coronavirus (COVID-19) on nose and throat swabs since 7 November 2020

Notes:

1. These results are provisional and subject to revision.

2. All estimates are subject to uncertainty, given that a sample is only part of the wider population. The model used to provide these estimates is a Bayesian model: these provide 95% credible intervals. A credible interval gives an indication of the uncertainty of an estimate from data analysis. 95% credible intervals are calculated so that there is a 95% probability of the true value lying in the interval.

3. Official reported estimates are plotted at a reference point believed to be most representative of the given week. Details of which day was used for each week can be found in the dataset that accompanies this bulletin.

4. Modelled estimates include all swab results that are available at the time the official estimates are produced. Additional swab tests that become available after this are included in subsequent models, meaning that modelled estimates can change slightly as additional data are included.

5. Official estimates should be used to understand the positivity rate for a single point in time. This estimate, based on the modelled estimate for the latest week, is our best and most stable estimate and is used in all previous outputs. The modelled estimate can be used to understand the recent trend. The modelling includes a set period of data and smooths the estimate over time.

Download the data

.xlsx

Notes for: Number of people in Northern Ireland who had COVID-19

1. This is based on model estimates from the reference point of the most recent week (12 to 18 December 2020), Wednesday 15 December 2020.

During the most recent week of the study¹, we estimate that 37,100 people in Scotland had the coronavirus (COVID-19) (95% credible interval: 28,900 to 46,300). This equates to 0.71% (95% credible interval: 0.55% to 0.88%) of the population in Scotland or around 1 in 140 people (95% credible interval: 1 in 180 to 1 in 115). The ratios in this bulletin are rounded to the nearest 5. Our modelling suggests that the percentage testing positive in Scotland has decreased in the most recent week. This is based on exploratory modelling of throat and nose swab results.

We have presented the weighted fortnightly estimates in Figure 11. These data underpin the modelling. The percentage of people testing positive in the latest 14-day period (5 December to 18 December 2020) was 0.97% (confidence interval: 0.77% to 1.20%).

Figure 10: The percentage testing positive in Scotland has decreased in the most recent week

Estimated percentage of the population in Scotland testing positive for the coronavirus (COVID-19) on nose and throat swabs since 7 November 2020

Notes:

1. These results are provisional and subject to revision.

2. All estimates are subject to uncertainty, given that a sample is only part of the wider population. The model used to provide these estimates is a Bayesian model: these provide 95% credible intervals. A credible interval gives an indication of the uncertainty of an estimate from data analysis. 95% credible intervals are calculated so that there is a 95% probability of the true value lying in the interval.

3. Official reported estimates are plotted at a reference point believed to be most representative of the given week. Details of which day was used for each week can be found in the dataset that accompanies this bulletin.

4. Modelled estimates include all swab results that are available at the time the official estimates are produced. Additional swab tests that become available after this are included in subsequent models, meaning that modelled estimates can change slightly as additional data are included.

5. Estimates for Scotland do not include data for Orkney, Shetland and the Western Isles due to operational issues. We are working to resolve these issues as soon as possible.

6. Official estimates should be used to understand the positivity rate for a single point in time. This estimate, based on the modelled estimate for the latest week, is our best and most stable estimate and is used in all previous outputs. The modelled estimate can be used to understand the recent trend. The modelling includes a set period of data and smooths the estimate over time.

Download the data

.xlsx

The estimates for non-overlapping 14-day periods (which underpin our modelled official estimates) are presented in Figure 11. These 14-day estimates are provided for context. The data are also included in the accompanying dataset.

Notes for: Number of people in Scotland who had COVID-19

1. This is based on model estimates from the reference point of the most recent week (12 to 18 December 2020), Wednesday 15 December 2020.

This analysis was produced by Sarah Walker at the University of Oxford and looks at the prevalence of the new variant of the coronavirus (COVID-19) across the UK.

Swabs are tested for three genes present in the coronavirus: N protein, S protein and ORF1ab. Each swab can have any one, any two or all three genes detected. Positives are those where one or more of these genes is detected in the swab other than tests that are only positive on the S-gene, which is not considered a reliable indicator of the virus if found on its own.

The new variant of COVID-19 has genetic changes in the S-gene. This means the S-gene is no longer detected in the current test, and cases that would have previously been positive on all three genes are now positive only on the ORF1ab and the N-gene (not the S-gene).

There are also other reasons why a swab may be positive for only these two genes, including lower viral load in the sample, which is why we have always seen a small percentage of this type of positive result. Absence of the S-gene appears to have become a reliable indicator of the new variation in COVID-19 from mid-November, based on the higher levels of virus in these type of positives after this date. Prior to that, the data should not be read as being an indicator of the variant.

There has recently been an increase in the percentage of positive cases where only the ORF1ab and N-genes were found and a decrease in the percentage of cases with all three genes. We can use this information to approximate the growth of the new variant.

Data should be treated with caution. In particular, there are small numbers of positives detected in Wales, Northern Ireland and Scotland leading to considerable uncertainty surrounding these estimates. There are further uncertainties given that not all cases that are positive on the ORF1ab and N-genes will be the new variant.

Figure 12 shows the percentages of positive cases during the most recent period (14 to 18 December) where only the ORF1ab and N-genes were found, that are compatible with the new variant of the virus. The highest percentages are seen in London, the South East, and the East of England. In contrast, the percentages of cases compatible with the new variant remain relatively low in other regions at present; this can also be seen in the positivity rates of new variant compatible by region.

We have recently published modelled estimates of the percentage of positive cases compatible with the new variant and other variants for England and regions of England, and for Wales, Northern Ireland and Scotland.

The Coronavirus (COVID-19) Infection Survey analysis was produced by the Office for National Statistics (ONS) in collaboration with our research partners at the University of Oxford, the University of Manchester, Public Health England (PHE) and Wellcome Trust. Of particular note are:

• Sarah Walker – University of Oxford, Nuffield Department for Medicine: Professor of Medical Statistics and Epidemiology and Study Chief Investigator

• Koen Pouwels – University of Oxford, Health Economics Research Centre, Nuffield Department of Population Health: Senior Researcher in Biostatistics and Health Economics

• Thomas House – University of Manchester, Department of Mathematics: Reader in Mathematical Statistics

These statistics have been produced quickly in response to developing world events. The Office for Statistics Regulation, on behalf of the UK Statistics Authority, has reviewed them against several important aspects of the Code of Practice for Statistics and regards them as consistent with the Code's pillars of trustworthiness, quality and value.

The estimates presented in this bulletin contain uncertainty. There are many sources of uncertainty, including uncertainty in the test, in the estimates and in the quality of data collected in the questionnaire. Information on the main sources of uncertainty are presented in our methodology article.