- 30 Oct 2020
The COVID-19 Infection Survey aims to establish:
- 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
Samples from the survey are not yet large enough to support more detailed analysis than is provided below.
Proportion of people in Scotland testing positive for COVID-19
It is estimated that in the most recent 14 day period (10 October to 23 October), the percentage of the population in Scotland testing positive for the coronavirus (COVID-19) was 0.71% (with a 95% confidence interval of 0.48% to 1.01%). This equates to around 1 in 140 people (95% confidence interval: 1 in 210 to 1 in 100). In the same 14 day period, it is estimated that an average of 37,400 people in Scotland had COVID-19 (95% credible interval: 25,300 to 53,300).
For the previous non-overlapping 14 day period (26 September to 9 October), the percentage of the population in Scotland testing positive for the coronavirus (COVID-19) was estimated to be 0.31% (with a 95% confidence interval of 0.12% to 0.64%).
Due to the relatively small number of tests and positive swab results within our sample, the confidence intervals are wide and therefore results should be interpreted with caution. It is too early to comment on any trend on the proportion of the population testing positive for COVID-19 in Scotland.
Samples from the survey are not yet large enough to support more detailed analysis than is provided here. Fieldwork is being scaled up with the aim of testing 15,000 participants per fortnightly period. This will enable more detailed analysis, such as examining the characteristics of those testing positive for COVID-19, establishing the average number of new infections per week, and the number of people who test positive for antibodies, to indicate how many people are ever likely to have had the infection.
Estimates of the total national proportion of the population testing positive for COVID-19 are weighted to be representative of the population in Scotland that live in private-residential households in terms of age (grouped), sex, and region. The population used in this analysis relates to the community population aged two years and over.
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
- identifying differences in numbers of positive cases between different regions
- 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
- producing a UK estimate; ONS now have estimates for England, Scotland, Wales and Northern Ireland, but these cannot be added up or averaged to understand the UK infection rate
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.
It is important to note that there is a degree of uncertainty with these estimates. 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
95% credible intervals can be interpreted as - provided that the model is correct - there being a 95% probability that the true value being estimated lies within the credible interval. Again, a wider interval indicates more uncertainty in the estimate.
The results are for private households only, and do not apply to those in hospitals, care homes or other institutional settings.
The Infection Survey bulletins available on the ONS website also include results for England, Wales and Northern Ireland.
Further details on the methodology used can be found on the ONS website.