ONS Coronavirus (COVID-19) Infection Survey – antibody data - 16 February 2021

This data refers to the presence of antibodies to the Coronavirus (COVID-19) within the community population; community in this instance refers to private residential households, and it excludes those in hospitals, care homes and/or other institutional settings.

This article presents analysis on past infection and/or vaccination, which is defined as testing positive for antibodies to SARS-CoV-2 based on findings from the COVID-19 Infection Survey. SARS-CoV-2 is the scientific name given to the specific virus that causes COVID-19.

The Office for National Statistics (ONS) have changed the way antibody estimates are reported and are now presenting weighted estimates for 28-day periods of antibody positivity, rather than monthly estimates. This approach will allow for more frequent updates and antibody data will now be published fortnightly. Please note that these 28 day estimates cannot be directly compared with previously published monthly antibody estimates.

Estimated proportion of people in Scotland who would have tested positive for COVID-19 antibodies in the 28 days up to 01 February 2021

In the 28 days up to 01 February 2021, it is estimated that 11.7% of the population in Scotland would have tested positive for COVID-19 antibodies from a blood sample. A 95% confidence interval for this estimate is 10.3% to 13.2%.

It is estimated that, at any given time in this 28-day period, 521,000 people in Scotland aged 16 and over would have tested positive for COVID-19 antibodies (95% confidence interval: 459,000 to 587,000). This equates to around 1 in 9 people aged 16 and over (95% confidence interval: 1 in 10 to 1 in 8).

The population used in this analysis relates to the community population aged 16 years and over. These figures exclude those living in hospitals, care homes and other institutional settings.

Figure 1: Estimated percentage of the population who would have tested positive for COVID-19 antibodies in 28-day periods from 15 September 2020 to 01 February 2021 in Scotland, including 95% confidence intervals

Estimated proportion of people in Scotland who would have tested positive for antibodies, by age group

In the 28 days up to 01 February 2021 it is estimated that 11.6% of people aged 80 and over would have tested positive for antibodies (95% confidence interval: 5.6% to 20.6%). In other age groups, between 7.7% and 15.5% of people would have tested positive for antibodies.

There is high uncertainty around these estimates due to the relatively small number of people included in this analysis, so caution should be taken in interpreting the results.

Figure 2: Estimated percentage of the population who would have tested positive for COVID-19 antibodies in the 28 days up to 01 February 2021 split by age group, including 95% confidence intervals

Methodology and further information

The analysis in this section of the article is based on blood test results taken from a randomly selected subsample of individuals aged 16 years and over, which are used to test for antibodies against SARS-CoV-2. This can be used to identify individuals who have had the infection in the past or have developed antibodies as a result of vaccination.

It takes between two and three weeks after infection or vaccination for the body to make enough antibodies to fight the infection. Antibodies remain in the blood at low levels, although these levels can decline over time to the point that tests can no longer detect them. Having antibodies can help to prevent individuals from getting the same infection again.

The presence of antibodies is measured to understand who has had coronavirus (COVID-19) in the past and the impact of vaccinations. Once infected, the length of time antibodies remain at detectable levels in the blood is not fully known. It is also not yet known how having detectable antibodies, now or at some time in the past, affects the chance of getting COVID-19 again.

These statistics refer to infections reported in the community, by which we mean private households. These figures exclude infections reported in hospitals, care homes and/or other institutional settings. The population used in this analysis relates to the community population aged 16 years and over. It should be emphasised that this data does not include those that live in care homes, one of the priority groups identified by the Joint Committee on Vaccination and Immunisation (JCVI).

Weighted 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.

The full article on antibody test results published by the Office for National Statistics on 16 February 2021, which includes antibody information for England, Wales and Northern Ireland, can be accessed here.

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.