Coronavirus (COVID-19): ONS Infection Survey – headline results – 18 June 2021

The COVID-19 Infection Survey aims to measure:

• how many people test positive for COVID-19 infection at a given point in time, regardless of whether they report experiencing coronavirus symptoms
• the average number of new infections per week over the course of the study
• the number of people who test positive for antibodies, to indicate how many people are ever likely to have had the infection or have been vaccinated

The Office for National Statistics (ONS) publish estimates for England, Wales, Northern Ireland and Scotland on their website.

The underlying data displayed in the charts in this publication is available in the reference tables on the ONS website.

All results are provisional and are subject to revision.

When positivity rates are low, it is not possible to produce age over time analysis by single year of age for all four UK countries because the numbers of people testing positive are too small for any estimate to be robust. As a result, ONS are not currently updating these data. Previously published data are available in the accompanying datasets for each UK country

ONS regularly review the methods and survey design as part of an ongoing quality assurance process. The method used to estimate incidence uses several weeks’ data to provide the latest estimate of new infections. Due to lower numbers of people testing positive over the last several weeks compared with earlier in the year, estimates of incidence (last published 7 May 2021) are being reviewed. This review ensures that the estimates provided continue to be of high quality. For more information on how estimates of incidence are calculated please see COVID-19 Infection Survey: methods and further information.

Main Points

In the week 6 to 12 June 2021, the estimated percentage of the community population (private households) testing positive for COVID-19 in Scotland was 0.17% (95% credible interval: 0.09% to 0.27%). The trend in the percentage of people testing positive in the community remains uncertain in the most recent week.

This equates to an estimated 8,800 people in the community population in Scotland that had COVID-19 at any given time (95% credible interval: 4,900 to 14,000), or around 1 in 600 people (95% credible interval: 1 in 1,070 to 1 in 380).

In the week 6 to 12 June 2021, estimates for the other nations of the UK are as follows:

• in England, the percentage of people testing positive in the community continued to increase in the most recent week to 0.19% (95% credible interval: 0.16% to 0.23%).
• in Wales, the percentage of people testing positive in the community remains low; with positivity estimated to be 0.07% (95% credible interval: 0.02% to 0.14%).
• in Northern Ireland, the trend in the percentage of people testing positive in the community remains uncertain in the most recent; with positivity estimated to be 0.16% (95% credible interval: 0.06% to 0.32%).

Modelled estimate of the proportion of the community population in Scotland that had the coronavirus (COVID-19)

It is estimated that in the most recent week (6 to 12 June 2021), the percentage of the community population (private households) in Scotland that had the coronavirus (COVID-19) was 0.17%. A 95% credible interval for this figure is 0.09% to 0.27%.

In the same week, it is estimated that at any given time 8,800 people in the community in Scotland had COVID-19. A 95% credible interval for this figure is 4,900 to 14,000. This equates to around 1 in 600 people (95% credible interval: 1 in 1,070 to 1 in 380).

In Scotland, the trend in the percentage of people testing positive for COVID-19 in the community population remains uncertain in the most recent week.

Modelled daily estimates of the percentage of people testing positive for COVID-19, and accompanying credible intervals, are represented in Figure 1 by the blue line and grey shading. The model smooths the series to understand the trend and is revised each week to incorporate new test results. Modelled daily estimates are used to calculate the official reported estimate.

Official reported estimates of the percentage of people testing positive for COVID-19, are based on the modelled estimate for the midpoint of the most recent week at the time of publication. Official reported estimates, and accompanying credible intervals, are represented in Figure 1 and Figure 2 by the point estimates (blue circles). In Figure 2, pale blue circles denote 14-day weighted estimates while the official reported weekly estimates are denoted by dark blue circles.

Figure 1: Modelled daily estimates and official reported estimates of the percentage of the community population in Scotland testing positive for COVID-19 between 2 May and 12 June 2021, including 95% credible intervals (see notes 2,3,4,5,6)

Figure 2 shows the trend in the official weekly reported estimates of the percentage of the community population testing positive for COVID-19 between 3 October 2020 and 12 June 2021. As shown in Figure 2, official reported estimates of positivity were decreasing since mid-March, followed by an increase in mid-May. Since then, trends have been uncertain week by week. All official reported estimates of positivity displayed in this chart are available in the accompanying dataset on the ONS website.

Figure 2: Official reported estimates of the percentage of the community population in Scotland testing positive for COVID-19 between 3 October 2020 and 12 June 2021, including 95% credible intervals (see notes 3,4,5,6)

Modelled estimate of the proportion of the community population testing positive for COVID-19 in each of the four nations of the UK  

In the week ending 12 June 2021:

• in Scotland, the trend in the percentage of people testing positive in the community remained uncertain.
• in England, the percentage of people testing positive in the community continued to increase in the most recent week.
• in Wales, the percentage of people testing positive in the community remains low.
• in Northern Ireland, the trend in the percentage of people testing positive in the community remained uncertain.

Figure 3: Modelled daily estimates of the percentage of the community population testing positive for COVID-19 in each of the four nations of the UK, between 2 May and 12 June 2021, including 95% credible intervals (see notes 2,3,4,5,6)

*Northern Ireland

Table 1: Modelled estimates of the proportion of the community population testing positive for COVID-19, and corresponding 95% credible intervals, between 6 and 12 June 2021 for the four nations of the UK (See notes 1,3,4,5)

Nation	Estimated percentage of the population that had COVID-19	Estimated number of people who had COVID-19	Estimated ratio of people who had COVID-19
England	0.19% (0.16% to 0.23%)	105,000 (88,500 to 124,000)	1 in 520 (1 in 620 to 1 in 440)
Northern Ireland	0.16% (0.06% to 0.32%)	3,000 (1,100 to 5,900)	1 in 610 (1 in 1,640 to 1 in 310)
Scotland	0.17% (0.09% to 0.27%)	8,800 (4,900 to 14,000)	1 in 600 (1 in 1,070 to 1 in 380)
Wales	0.07% (0.02% to 0.14%)	2,000 (700 to 4,200)	1 in 1,500 (1 in 4,340 to 1 in 720)

Estimates of the percentages of those testing positive for COVID-19 by variant

The World Health Organisation (WHO) have suggested new names for Variants of Concern and Variants of Interest to assist with public discussions of the variants, which can be found as a table on the WHO website.

The Alpha variant (B.1.1.7) of COVID-19 has changes in one of the three genes that COVID-19 swab tests detect, known as the S-gene. This means in cases compatible with the Alpha variant, the S-gene is not detected by the current test and has the pattern ORF1ab+N (S gene negative) in the main variant analysis.

Other variants of concern – including both the Delta variant (B.1.617.2) and the Beta variant (B.1.351) – are positive on all three genes, with the pattern ORF1ab+S+N. Based on recent information from genomic sequencing and Test and Trace, ONS state that it is likely that most ORF1ab+S+N cases will be the Delta variant. Therefore, if there is an increase in the prevalence of any of these strains, this will show up in the analysis as an increase in cases “Compatible with the Delta variant”.

This main variant analysis can therefore differentiate between these two groups of variants (ORF1ab+N positive or ORF1ab+S+N positive), but cannot differentiate between variants that have the same gene pattern for the three genes that COVID-19 swab tests detect. More information on individual variants and where they were first detected is available on the government variant dashboard.

Other variants, including the Eta variant (B.1.525), may also have the same pattern of gene positivity as the Alpha variant. At present this variant is rare in the UK so this group will continue to be described as compatible with the Alpha variant, but ONS will continue to keep this under review. You can read more about the UK variant in the blog published by ONS.

In the week ending 12 June 2021, the trend in the percentage of people in the community population testing positive that are compatible with the Alpha variant (B.1.1.7) was uncertain in Scotland, England and Northern Ireland, and remained low in Wales.

In the same week, the trend in the percentage of people in the community testing positive that are compatible with the Delta variant (B.1.617.2) was uncertain in Scotland and Northern Ireland, continued to increase in England and remained low in Wales.

Detailed variant analysis is no longer included in the Scottish Government COVID-19 Infection Survey publication. This data will continue to be published in the accompanying reference tables on the ONS website. Trends in variant categories will continue to be monitored over the coming weeks and the charts will be reintroduced into the publication based on the degree of uncertainty in the estimates and the direction of the trend.

Whole genome sequencing is undertaken on positive tests from this survey, where possible. More information on this can be found in previous publications on the ONS website.

This analysis was produced by research partners at the University of Oxford.

Further information

A technical article on positivity after vaccination (UK) was published on 17 June on the ONS website.

The latest estimate of the proportion of community population aged 16 and over in Scotland who would have tested positive for COVID-19 antibodies was published on 9 June 2021 on the Scottish Government website and ONS website.

An article on the prevalence of ongoing symptoms following coronavirus (COVID-19) infection in the UK was published on the ONS website on 4 June 2021. The article includes estimates of the prevalence of self-reported "long COVID", and the duration of ongoing symptoms following confirmed coronavirus infection, using UK Coronavirus (COVID-19) Infection Survey data to 2 May 2021.

An article on how often individuals are reporting social contact with other people outside their own household, either socially distanced or physical contact was published on 20 May 2021 on the Scottish Government website and ONS website.

An article on the symptom profile of strong positive cases in the UK was also published on 20 May 2021. The article includes estimates of the percentage of people testing positive that reported symptoms and the likelihood of reporting specific symptoms by nation. Analysis for Scotland was last published on the Scottish Government website on 5 May 2021. The article on the ONS website also includes analysis on the likelihood of testing positive for COVID-19 by patient-facing or non-patient facing job roles.

How this data can be used

The data can be used for:

• estimating the number of current positive cases in the community, including cases where people do not report having any symptoms
• estimating the number of new cases and change over time in positive cases

The data cannot be used for:

• measuring the number of cases and infections in care homes, hospitals and other institutional settings
• estimating the number of positive cases and new infections in smaller geographies, such as towns and cities
• providing information about recovery time of those infected

Methodology

The results are based on nose and throat swabs provided by participants to the study, obtained from fieldwork which started in Scotland on 21 September 2020.

The results are for private households only, and do not apply to those in hospitals, care homes or other institutional settings. The population used in this analysis relates to the community population aged two years and over.

In the latest six-week period, there were 54,076 swab tests from 31,135 people, with a total of 60 positive tests in 56 people from 48 households. In the latest two-week period, there were 16,250 swab tests from 15,252 people, with a total of 23 positive tests in 23 people from 23 households.

The COVID-19 Infection Survey bulletins and datasets available on the ONS website also include results for England, Wales and Northern Ireland.

The Welsh Government and the Department of Health in Northern Ireland also publish results from the COVID-19 Infection Survey for Wales and Northern Ireland respectively:

• Welsh Government
• Department of Health in Northern Ireland

Further details on the methodology used can be found on the ONS website.

Notes

1. Any ratios presented are rounded to the nearest 10. These ratios do not represent a person's risk of becoming infected, since risk of infection depends on a number of factors such as contact with others or whether a person has been vaccinated.
2. There is more uncertainty around estimates for the latest three reported days (as shown by the vertical dashed line), as lab results for this period are still being processed at the time of publication. Additional swab tests that become available after this publication are included in subsequent models, meaning that modelled estimates can change as additional data is included.
3. Modelled estimates are not directly comparable with the 14-day weighted estimates provided in the accompanying dataset on the ONS website. The 14-day weighted estimates underpin the modelled estimates and are provided for context. 14-day weighted estimates are not directly comparable with the weekly modelled estimates due to the differing methodology, however they have been included in Figure 2 as they were reported as the official estimates for Scotland before the weekly modelled estimates became available.
4. 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.
5. Because of the relatively small number of tests and a low number of positives in the sample, credible intervals are wide and therefore results should be interpreted with caution.
6. The blue line and shading represent the modelled trend and credible intervals based on the latest data. The point estimates and error bars represent the official weekly estimates and their credible intervals, which are based on the modelled estimate for the midpoint of the week at the time of publication.