Coronavirus (COVID-19): ONS Infection Survey - headline results - 14 May 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.

Due to low positivity rates, ONS are not able to produce sub-regional positivity estimates and analysis by single year of age for the four UK countries for this publication.

Due to lower positivity rates, ONS are also carrying out some additional checks on estimates of incidence (last published 7 May 2021). Therefore, incidence estimates will not be updated in this publication. 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 2 to 8 May 2021, the estimated percentage of the community population (private households) testing positive for COVID-19 in Scotland was 0.08% (95% credible interval: 0.04% to 0.15%). The percentage of people testing positive in the community has continued to decrease in the most recent week.

This equates to an estimated 4,200 people in the community population in Scotland that had COVID-19 at any given time (95% credible interval: 1,900 to 7,700), or around 1 in 1,250 people (95% credible interval: 1 in 2,730 to 1 in 690).

In the week 2 to 8 May 2021, estimates for the other nations of the UK are as follows:

• in England, the percentage of people testing positive in the community population has continued to decrease in the most recent week to 0.07% (95% credible interval: 0.06% to 0.09%)
• in Northern Ireland, the percentage of people testing positive in the community population has decreased in the most recent two weeks to 0.07% (95% credible interval: 0.02% to 0.16%), but the trend is uncertain over the most recent week.
• in Wales, the percentage of people testing positive in the community population appears to have decreased in the most recent week to 0.02% (95% credible interval: 0.00% to 0.06%), and positivity rates continue to be very low.

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 (2 to 8 May 2021), the percentage of the community population (private households) in Scotland that had the coronavirus (COVID-19) was 0.08%. A 95% credible interval for this figure is 0.04% to 0.15%.

In the same week, it is estimated that at any given time 4,200 people in the community population had COVID-19. A 95% credible interval for this figure is 1,900 to 7,700. This equates to around 1 in 1,250 people (95% credible interval: 1 in 2,730 to 1 in 690).

In Scotland, the percentage of people testing positive for COVID-19 in the community population has continued to decrease in the most recent week, as shown in Figure 1.

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 28 March and 8 May 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 8 May 2021. As shown in Figure 2, official reported estimates of positivity have decreased since mid-March. 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 8 May 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 8 May 2021, the number of people testing positive in the community continued to decrease in Scotland and England and appears to have decreased in Wales. Positivity rates are currently very low in Wales, which means that it is difficult to identify trends since they are affected more easily by small changes in the number of people testing positive from week to week. The number of people testing positive in Northern Ireland decreased in the two weeks to 8 May 2021, but the trend for the most recent week is 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 28 March and 8 May 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 2 and 8 May 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	0.07% (0.06% to 0.09%)	40,800 (31,900 to 50,900)	1 in 1,340 (1 in 1,710 to 1 in 1,070)
Northern Ireland	0.07% (0.02% to 0.16%)	1,300 (300 to 3,000)	1 in 1,430 (1 in 5,360 to 1 in 610)
Scotland	0.08% (0.04% to 0.15%)	4,200 (1,900 to 7,700)	1 in 1,250 (1 in 2,730 to 1 in 690)
Wales	0.02% (0.00% to 0.06%)	700 (100 to 1,900)	1 in 4,230 (1 in 22,280 to 1 in 1,580)

Estimate of the percentage of those testing positive for COVID-19 whose test results were compatible with the new UK variant

A new variant of COVID-19 was identified in the UK in mid-November 2020. The UK variant (B.1.1.7) of COVID-19 has changes in one of the three genes which coronavirus swab tests detect, known as the S-gene. This means in cases compatible with the UK variant, the S-gene is not detected by the current test. Other variants, including B.1.525 (first identified in Nigeria), may also have this same pattern of gene positivity. At present these are rare in the UK so we continue to describe this group as compatible with the UK variant, but ONS will continue to keep this under review. You can read more about the UK variant in the blog published by ONS.

The trend in the percentage of people in the community population testing positive that are compatible with the UK variant decreased in Scotland and England in the week ending 8 May 2021. The trend was uncertain in Wales and Northern Ireland in the same week.

Detailed analysis on the UK variant 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 different variants will continue to be monitored over the coming weeks and the charts will be reintroduced into the publication if there is a variant that can be identified using survey tests that appears to be affecting the trends in the percentage of people testing positive for COVID-19.

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

Further information

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 13 May 2021 on the Scottish Government website and ONS website.

An article on the symptom profile of strong positive cases in the UK was published on the ONS website on 5 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 published on the Scottish Government website. The article on the ONS website also includes analysis on the likelihood of testing positive for COVID-19 by work location, mode of travel to work and reported ability to socially distance in the workplace for the UK.

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 22 April 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 1 April 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 6 March 2021.

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 49,893 swab tests from 30,184 people, with a total of 88 positive tests in 83 people from 66 households. In the latest two-week period, there were 14,859 swab tests from 13,971 people, with a total of 12 positive tests in 10 people from 8 households.

The Infection Survey bulletins 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.
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.