Coronavirus (COVID-19): ONS Infection Survey – characteristics data for Scotland – 19 January 2022

ONS Coronavirus (COVID-19) Infection Survey – Characteristics Data for Scotland – 19 January 2022

The article is based on findings from the Office for National Statistics (ONS) COVID-19 Infection Survey.

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 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 those living in private residential households aged two years and over.

The Office for National Statistics (ONS) publish analysis of the characteristics of those testing positive for COVID-19 in England, Wales, Northern Ireland, Scotland and the UK on their website.

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

Main points

This week, the ONS have reintroduced analysis on COVID-19 symptoms over time for Scotland. This analysis was last published on 21 October 2021 by the ONS and the Scottish Government.

In Scotland, 63.5% of people living in private residential households who tested positive for COVID-19 with a strong positive test between 1 December 2020 and 31 December 2021 reported having any symptoms (95% confidence interval: 61.3% to 65.6%).

The most commonly experienced symptoms in those living in private residential households in Scotland were a cough, fatigue or weakness, and a headache.

In Scotland, adults had fewer socially distanced contacts but slightly more physical contacts in the fortnight ending 31 December 2021, compared to previous fortnights.

In the same fortnight, children reported fewer physical and socially distanced contacts with other children (corresponding to the school Christmas holidays), but slightly more socially distanced and physical contacts with people aged over 70 years, compared to previous fortnights.

Symptom profile of people who tested positive for COVID-19 in Scotland

This analysis considers individuals with any positive test, including repeated positive tests, that had a high viral load (Ct value (please see footnote 2) less than 30) between 1 December 2020 and 31 December 2021 in Scotland.

Individuals taking part in the survey were asked at each visit whether they had experienced a range of possible symptoms in the seven days before they were tested, and also separately whether they felt that they had symptoms compatible with COVID-19 infection in the last seven days. This analysis considers all symptoms reported at visits within 35 days of the first positive test of the episode.

This includes symptoms reported even when there is a negative test within this timeframe or a positive test with a higher Ct value. Data for the whole UK, for each nation and for the UK split by variant is available in the article published on the ONS website, along with more details on the methods used in this analysis.

The UK wide analysis shows that between 9 and 31 December 2021, people with Omicron compatible infections were substantially less likely than people with Delta compatible infections to report loss of taste or loss of smell.

The comparison of Omicron compatible and Delta compatible infections is based on the period between 9 and 31 December 2021. It is possible that Omicron infections in this period are disproportionately earlier stage infections. If this is the case then this analysis may underestimate the percentage of Omicron cases which are symptomatic in December 2021, although any such underestimation would likely not be large enough to cancel out substantial differences between Omicron and Delta variants.

In Scotland, 63.5% of people living in private residential households who tested positive for COVID-19 with a strong positive test between 1 December 2020 and 31 December 2021 reported having any symptoms (95% confidence interval: 61.3% to 65.6%).

The data presented are unweighted percentages of people with any positive test result that had a Ct value less than 30.

In all four UK nations, over half the people who are estimated to have tested positive for COVID-19 with a strong positive test reported having symptoms within 35 days of the test.

Results should be interpreted with caution for Scotland, Wales and Northern Ireland because of smaller sample sizes of people who have a strong positive test (Ct less than 30) than for England, resulting in wider confidence intervals.

Figure 1: Unweighted percentage of people with a strong positive test for COVID-19 who reported having any symptoms and no symptoms, in each of the four nations of the UK, from 1 December 2020 to 31 December 2021 including 95% confidence intervals

Figure 2 shows that people who tested positive for COVID-19 with a strong positive test were more likely to report ‘classic’ Covid-19 symptoms (cough, fever, loss of taste or loss of smell) than gastrointestinal symptoms, or loss of taste or smell only.

Figure 2: Unweighted percentage of people with a strong positive test for COVID-19, by grouped symptoms, from 1 December 2020 to 31 December 2021 in Scotland, including 95% confidence intervals

 

Figure 3 shows that a cough, fatigue or weakness, and a headache were the most common symptoms reported in strong positive COVID-19 cases in Scotland. Diarrhoea, abdominal pain, and nausea or vomiting were less commonly reported symptoms in strong positive COVID-19 cases.

Figure 3: Unweighted percentage of people with a strong positive test for COVID-19, by symptom, from 1 December 2020 to 31 December 2021 in Scotland, including 95% confidence intervals

 

Socially distanced and physical contacts - Scotland

This analysis looks at how often individuals are reporting social contact with other people outside their own household, either socially distanced or physical contact. As part of survey visits, individuals were asked how many people outside their household, aged 17 years and under, 18 to 69 years, and 70 years and over, they had had contact with up to seven days prior to each study visit.

Contact refers to either of the following:

• socially distanced contact – direct contact with social distancing only
• physical contact – physical contact, such as a handshake or personal care, including wearing personal protective equipment (PPE)

In this article, fortnightly estimates are available for the time period from 18 to 31 December 2021. Data on socially distanced and physical contacts for Scotland was previously presented on 16 December 2021.

Estimates have been weighted to be representative of the total population in Scotland. Analysis includes all people taking part in the survey. The survey only includes those living in private residential households. Contact analysis is presented for school-age children (age two years to school year S4) and adults (school year S5 and above).

The number of contacts is reported in the following groups:

• 0 (no reported contacts)
• 1 to 5 (reported contacts)
• 6 to 10 (reported contacts)
• 11 to 20 (reported contacts)
• 21 or more (reported contacts)

School-age children

The proportions of school-age children reporting each category of number of physical and socially distanced contacts are shown in Figures 4 and 5 respectively.

In Scotland, children reported fewer physical and socially distanced contacts with other children (corresponding to the school Christmas holidays) in the fortnight ending 31 December 2021, compared to previous fortnights. However, children reported slightly more socially distanced and physical contacts with people aged over 70 years.

In Figures 4 to 7, each bar represents one two-week period, denoted by the end date of that period. For example, 31 December 2021 denotes the estimate relating to 18 to 31 December 2021.

Figure 4: Proportion of school-age children by number of physical contacts with different age groups, from 26 September 2020 to 31 December 2021

 

Figure 5: Proportion of school-age children by number of socially distanced contacts with different age groups, from 26 September 2020 to 31 December 2021

 

Adults

The proportions of adults reporting each category of number of physical and socially distanced contacts are shown in Figures 6 and 7 respectively.

In Scotland, adults had fewer socially distanced contacts but slightly more physical contacts in the fortnight ending 31 December 2021, compared to previous fortnights.

Figure 6: Proportion of adults by number of physical contacts with different age groups, from 26 September 2020 to 31 December 2021

 

Figure 7: Proportion of adults by number of socially distanced contacts with different age groups, from 26 September 2020 to 31 December 2021

 

Methodology and further information

1. The population relates to those living in private residential households aged two years and over, and does not include people in hospital, care homes or students in halls of residence, where rates of COVID-19 infection are likely to be different.

2. The symptom profile analysis looks at symptoms associated with positive episodes (including repeated positive tests) with any Ct value in the episode below 30. This is to exclude the possibility that symptoms are not identified when an individual tests positive as it is very early on or later on in the infection. You can find more information on Ct values in a paper written by academic partners at the University of Oxford.

3. The symptom profile analysis is based on data collected at each study visit where participants are asked to report their symptoms in the previous 7 days.

4. The symptom profile analysis shows the proportion of individuals testing positive who reported experiencing symptoms at study visits within 35 days of their first positive test.

5. Symptoms are self-reported and were not professionally diagnosed.

6. Because of the relatively small number of tests and a low number of positives in the sample, confidence intervals are wide and therefore results should be interpreted with caution.

7. SARS-CoV-2 is the scientific name given to the specific virus that causes COVID-19.

8. Estimates are provided with 95% confidence intervals to indicate the level of uncertainty around them. 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. Please note that the sampling method used in Northern Ireland is different to the other nations, inviting only people who have previously participated in a Northern Ireland Statistics and Research Agency (NISRA) survey, which could result in a sample of individuals who are less likely to report symptoms.

The full article published by the Office for National Statistics on 19 January 2022, which includes data for England, Wales and Northern Ireland, can be accessed on the ONS website. The full article also includes analysis on reported symptoms across the UK.

More information about the COVID-19 Infection Survey in Scotland can be found on the information page on the Scottish Government website, and previous COVID-19 Infection Survey data for Scotland can be found in this collection.