Coronavirus (COVID-19): ONS Infection Survey – headline results – 6 May 2022

ONS Coronavirus (COVID-19) Infection Survey Results 6 May 2022

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 a shortened publication cycle for this release (to accommodate the early May 2022 bank holiday weekend), most recent analyses relating to number of new COVID-19 infections (incidence) and sub-regional positivity rates have not been updated this week. Previous incidence estimates and sub-regional positivity rates are available in the reference tables on the ONS website.

Main Points

In the week 25 April to 1 May 2022, the estimated percentage of the population living in private residential households testing positive for COVID-19 in Scotland was 3.55% (95% credible interval: 3.07% to 4.07%). The estimated percentage of people testing positive in Scotland continued to decrease in the most recent week.

In the same week, it is estimated that 186,700 people living in private residential households in Scotland had COVID-19 at any given time (95% credible interval: 161,800 to 214,300); this equates to around 1 in 30 people (95% credible interval: 1 in 35 to 1 in 25). The reported headline positivity estimates contain Omicron BA.1 and BA.2 variants and all other variants.

In the week 24 to 30 April 2022, estimates for the other nations of the UK are as follows:

• in England, the percentage of people testing positive continued to decrease: 2.91% (95% credible interval: 2.78% to 3.04%), equating to around 1 in 35 people (95% credible interval: 1 in 35 to 1 in 35).
• in Wales, the percentage of people testing positive continued to decrease: 4.33% (95% credible interval: 3.69% to 5.03%), equating to around 1 in 25 people (95% credible interval: 1 in 25 to 1 in 20).
• in Northern Ireland, the percentage of people testing positive decreased: 2.45% (95% credible interval: 1.90% to 3.07%), equating to around 1 in 40 people (95% credible interval: 1 in 55 to 1 in 35).

In Scotland, the estimated percentage of people testing positive for COVID-19 has decreased across all ages in recent weeks. However, the trend was uncertain for those aged over 75 years in the most recent week.

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

In this publication, the reference week for positivity estimates is 25 April to 1 May 2022 for Scotland and 24 to 30 April 2022 for England, Wales and Northern Ireland.

It is estimated that in the most recent week (25 April to 1 May 2022), the percentage of those living in private residential households in Scotland that had COVID-19 was 3.55%. A 95% credible interval for this figure is 3.07% to 4.07% (see note 4 for further information about credible intervals).

In the same week, the ONS estimate that 186,700 people living in private residential households in Scotland at any given time had COVID-19. A 95% credible interval for this figure is 161,800 to 214,300. This equates to around 1 in 30 people (95% credible interval: 1 in 35 to 1 in 25).

The percentage of people testing positive for COVID-19 in Scotland continued to decrease in the most recent week (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 and provide the best indication of trends over time.

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, and represent the best estimate at that point in time. 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 private residential population in Scotland testing positive for COVID-19 between 21 March and 1 May 2022, 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 those living in private residential households testing positive for COVID-19 between 3 October 2020 and 1 May 2022.

The estimated percentage of the private residential population testing positive for COVID-19 in Scotland increased between late-January and mid-March 2022. The estimate for the week 14 to 20 March 2022 was the highest estimate for Scotland since the survey began. Since late-March, the estimated percentage of people testing positive in Scotland has been decreasing. 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 private residential population in Scotland testing positive for COVID-19 between 3 October 2020 and 1 May 2022, including 95% credible intervals (see notes 3,4,5,6,7)      

 

Age analysis of the percentage of people testing positive for COVID-19 in Scotland

Modelled daily estimates of the percentage of the private residential population testing positive for COVID-19 in Scotland by single year of age, are available in the accompanying dataset on the ONS website.

In Scotland, the estimated percentage of people testing positive for COVID-19 has decreased across all ages in recent weeks. However, the trend was uncertain for those aged over 75 years in the most recent week.

Figure 3: Modelled daily estimates of the percentage of the private residential population in Scotland testing positive for COVID-19, by reference age, between 21 March and 1 May 2022, including 95% confidence intervals (see notes 2,5,6,8)  

    

The ONS publish an interactive chart in their weekly bulletin.

Caution should be taken in over-interpreting small movements in the latest trend.

More information on the percentage of people testing positive by age breakdown in Scotland can be found in the accompanying dataset for Scotland.

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

Figure 4 shows modelled daily estimates of the percentage of the private residential population testing positive for COVID-19 in each of the four nations of the UK.

The percentage of people testing positive for COVID-19 continued to decrease in England, Wales and Scotland, and decreased in Northern Ireland in the most recent week (25 April to 1 May 2022 for Scotland and 24 to 30 April 2022 for England, Wales and Northern Ireland).  

Figure 4: Modelled daily estimates of the percentage of the private residential population testing positive for COVID-19 in the four UK nations, between 21 March and 1 May for Scotland, and 21 March and 30 April for England, Wales and Northern Ireland, including 95% credible intervals (see notes 2,3,4,5,6)  

   

Modelled estimates of the proportion of the private residential population testing positive for COVID-19 for the most recent week can be found in Table 1.

Table 1: Modelled weekly estimates of the percentage of the private residential population testing positive for COVID-19 in the four UK nations, between 25 April and 1 May 2022 for Scotland, and 24 to 30 April 2022 for England, Wales and Northern Ireland, including 95% credible intervals (see notes 2,3,4,5,6)

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	2.91% (2.78% to 3.04%)	1,586,900 (1,516,200 to 1,659,000)	1 in 35 (1 in 35 to 1 in 35)
Northern Ireland	2.45% (1.90% to 3.07%)	44,900 (34,800 to 56,300)	1 in 40 (1 in 55 to 1 in 35)
Scotland	3.55% (3.07% to 4.07%)	186,700 (161,800 to 214,300)	1 in 30 (1 in 35 to 1 in 25)
Wales	4.33% (3.69% to 5.03%)	131,600 (112,200 to 152,800)	1 in 25 (1 in 25 to 1 in 20)

Modelled estimates of the percentage of the private residential population testing positive for COVID-19, by COVID-19 Infection Survey sub-regions

The ONS have created sub-regions across the UK for the purposes of this survey. In Scotland, these sub-regions are comprised of Health Boards. For a list of sub-regions in Scotland, see note 9.

Due to a shortened publication cycle for this release (to accommodate the early May 2022 bank holiday weekend), most recent analysis relating to sub-regional positivity rates has not been updated this week.

Previous sub-regional estimates for all four nations are available in the reference tables on the ONS website.

Number of new COVID-19 infections in Scotland

The ONS provides estimates of incidence, a measure of new Polymerase Chain Reaction (PCR)-positive cases in a given time period. This gives the rate at which new positives occur, and subsequently become detectable, within the population.

Due to a shortened publication cycle for this release (to accommodate the early May 2022 bank holiday weekend), most recent analysis relating to number of new COVID-19 infections (incidence) has not been updated this week.

For more information on how estimates of incidence are calculated, please see COVID-19 Infection Survey: methods and further information.

Previous incidence estimates are available in the reference tables on the ONS website.

Estimated percentages of those testing positive for COVID-19 by variant

The World Health Organization (WHO) have defined names for variants of concern. These are variants that the UK government has under surveillance.

Currently, variants under surveillance in the UK are:

• Omicron: B.1.1.529 (variant of concern), which includes sublineages BA.1, BA.2, BA.3, BA.4 and BA.5
• Delta: B.1.617.2 and its genetic descendants

The ONS publish weekly breakdowns of infections by variant and Cycle-threshold (Ct) values.

The "Cycle threshold", known as a Ct value, reflects the quantity of virus (also known as viral load) found in a swab test.  A lower Ct value indicates a higher viral load. The latest Ct values of COVID-19 positive tests are provided in the Coronavirus (COVID-19) Infection Survey: technical dataset.

Since March 2022, Omicron BA.2 compatible infections have been the most common in all UK countries, comprising 96.1% of all sequenced COVID-19 infections (in the four weeks to 24 April 2022).

The Omicron variant BA.1 has changes in one of the three genes that the coronavirus survey swab test detects, which means the S-gene is no longer detected. When there is a high viral load (for example, when a person is most infectious), not detecting the S-gene in combination with detecting the other two genes (ORF1ab and N-genes) is a reliable indicator of this Omicron BA.1 variant. However, as the viral load decreases (for example, if someone is near the end of their recovery from the infection), not detecting the S-gene is a less reliable indicator of this Omicron variant. The sub-variant Omicron BA1.1 also mostly has gene pattern ORF1ab + N. Therefore, gene pattern matching used in our main variant analysis cannot distinguish between Omicron BA.1 and Omicron BA1.1.

The Omicron variant BA.2 does not have changes in the S-gene, and therefore all three genes, or the S-gene and either ORF1ab or N, will usually be detected in infections with this variant.

During periods of change in COVID-19 variants we will include a breakdown of estimated infections by variant to illustrate how the estimated percentage of people infected in the population is changing by variant. When nearly all infections are compatible with a dominant variant, we will no longer include this breakdown.

The ONS last published main variant analysis in the bulletin on 22 April 2022. This showed a very high proportion of infections compatible with the BA.2 variant, so the ONS are no longer including a breakdown of infections by variant. The ONS will continue to monitor infections by variant and reintroduce the charts and analysis by gene pattern when considered helpful. More information on how the ONS measures variants from positive tests on the survey can be found in the Understanding COVID-19 Variants blog and the COVID-19 Infection Survey methodology article.

Genome Sequencing is produced by Wellcome Trust Sanger Institute and analysis is produced by research partners at the University of Oxford.

Further information

An article on the cumulative number of people in the UK who have tested positive for COVID-19 since the start of the survey was published on 22 April 2022 on the Scottish Government Website and ONS website. This release includes modelled cumulative percentages of the population who have tested positive for COVID-19 during the survey period by country.

An article on characteristics associated with third vaccination uptake was published on 21 April 2022 on the ONS website. This release includes modelled likelihood of receiving a third vaccination against COVID-19 by various screened characteristics, and age groups, for the UK.

An article on economic activity and social change in the UK was published on the ONS website on 5 May 2022. This release includes modelled estimates of the proportion of the workforce self-isolating because of coronavirus by work sector, and the proportion of the working age population self-isolating because of coronavirus by country.

An article on the proportion of those living in private residential households in Scotland who would have tested positive for COVID-19 antibodies was published on 4 May 2022 on the Scottish Government website and ONS website. This release includes modelled estimates of the percentage of people aged 11 years and over with antibodies against SARS-CoV-2.

An article on how often individuals in Scotland are reporting social contact with other people outside their own household (either socially distanced or physical contact) and estimates of the percentage of people testing positive that reported symptoms was published on 13 April 2022 on the Scottish Government website. The ONS also published an article on 13 April 2022 on the contacts analysis, as well as UK level analysis on the characteristics of people testing positive for COVID-19, on the ONS website.

A technical article on self-reported “long COVID” after two doses of a COVID-19 vaccine in the UK was published on the ONS website on 26 January 2022. The article explores the likelihood of participants in the UK reporting “long COVID” symptoms at least 12 weeks after COVID-19 infection, comparing CIS participants who had received two doses of a vaccine prior to infection with participants who were unvaccinated, using UK data to 30 November 2021.

An article on the prevalence of ongoing symptoms following COVID-19 infection in the UK was published on the ONS website on 7 April 2022. This release includes estimates of the prevalence of self-reported “long COVID”, and the duration of ongoing symptoms following confirmed COVID-19 infection, using UK data to 5 March 2022.

How this data can be used

The data can be used for:

• estimating the number of positive cases among the population living in private households, including cases where people do not report having any symptoms
• identifying differences in numbers of positive cases between UK countries and different regions in England
• 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/or other communal establishments
• 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 communal establishments. The population used in this analysis relates to the private residential population aged two years and over.

In Scotland, in the latest six-week period (21 March to 1 May 2022), there were 44,511 swab tests from 31,726 people, with a total of 2,615 positive samples in 2,580 people from 1,995 households. In the latest two-week period (18 April to 1 May 2022), there were 11,484 swab tests from 11,484 people, with a total of 425 positive samples in 425 people from 339 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. The ratios presented are rounded to the nearest 100 if over 1,000, to the nearest 10 if under 1,000, to the nearest 5 if under 100 and to 1 if under 20. This may result in credible intervals that appear to be similar to the estimated average ratio. 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 data set 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. 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.

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.

7. As there was no publication on 15 January 2021 there are no official estimates available for the week ending 9 January 2021. However, ONS conducted some additional analysis to assess what the estimate may have been, therefore this estimate is included in Figure 2, shown in light grey.

8. A confidence interval gives an indication of the degree of uncertainty of an estimate, showing the precision of a sample estimate. The 95% confidence intervals are calculated so that if we repeated the study many times, 95% of the time the true unknown value would lie between the lower and upper confidence limits. A wider interval indicates more uncertainty in the estimate.

9. The table below contains the composition of each CIS region in Scotland, by Health Board and Local Authority area. Local Authority areas map to the Health Board areas.

CIS Region Code	Health Boards	Local Authority Areas
123	NHS Grampian, NHS Highland, NHS Orkney, NHS Shetland and NHS Western Isles	Aberdeen City, Aberdeenshire, Argyll & Bute, Highland, Moray, Na h-Eileanan Siar, Orkney Islands, Shetland Islands
124	NHS Fife, NHS Forth Valley and NHS Tayside	Angus, Clackmannanshire, Dundee City, Falkirk, Fife, Perth & Kinross, Stirling
125	NHS Greater Glasgow & Clyde	East Dunbartonshire, East Renfrewshire, Glasgow City, Inverclyde, Renfrewshire, West Dunbartonshire
126	NHS Lothian	City of Edinburgh, East Lothian, Midlothian, West Lothian
127	NHS Lanarkshire	North Lanarkshire, South Lanarkshire
128	NHS Ayrshire & Arran, NHS Borders and NHS Dumfries & Galloway	Dumfries & Galloway, East Ayrshire, North Ayrshire, Scottish Borders, South Ayrshire

10. Estimates are based on confirmed positive test results. The remaining swabs are either negative, inconclusive or test failures. ONS are working with the laboratories to understand consistency in the identification of inconclusive results, that could be weak positive results. The impact of this on our estimates of positive infections is likely to be very small and unlikely to affect the trend.

11. Due to the timeliness of the data received from the laboratories and occurrence of public holidays there are gaps and overlaps between some of the official estimates, this does not impact the comparability of these estimates.