Coronavirus and behaviour of the vaccinated population after being in contact with a positive case in England: 22 to 27 November 2021

Behaviour of fully vaccinated individuals not required to self-isolate after being in contact with a positive case of COVID-19, from the COVID Test and Trace Contacts Behavioural Insights Survey. Experimental Statistics.

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Cyswllt:
Email Danielle Cornish and Hannah Mason

Dyddiad y datganiad:
17 December 2021

Cyhoeddiad nesaf:
To be announced

1. Main points

  • Data collected from 22 to 27 November 2021 show that the majority (93%) of respondents from the COVID Test and Trace Contacts Behavioural Insights Study reported they had taken a coronavirus (COVID-19) test since being contacted by NHS Test and Trace or via the app; of all respondents, over half (56%) reported that they had taken a PCR test and 37% had taken a Lateral Flow Test.

  • Around 1 in 10 of all respondents (9%) reported testing positive for COVID-19.

  • Of those who received two doses of the vaccine, 19% developed symptoms, compared with 8% of those who had received two doses and the booster dose; this was a statistically significant difference.

  • The majority (82%) of respondents said that double vaccinated contacts should take a PCR test after having been in contact with someone who has tested positive for COVID-19.

  • The proportion of respondents that reported they were currently self-isolating was significantly lower in late November 2021 (6%) than in late October 2021 (15%).

  • Around 29% felt the current isolation guidance for those who are double vaccinated was insufficient to keep the public safe and around three-fifths (60%) reported taking additional measures to keep themselves and others safe, beyond government guidelines and recommendations.

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The statistics presented are Experimental Statistics, so care needs to be taken when interpreting them. It is worth noting this survey has a relatively small sample size of 918. Please note, the data in this bulletin were collected prior to the changes to self-isolation policy based on the Omicron variant. Changes to policy were introduced from 30 November 2021.

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2. Glossary

Contacts not required to self-isolate

From 16 August 2021, close contacts of someone with coronavirus (COVID-19) were not required to self-isolate if they had been fully vaccinated. Fully vaccinated refers to having been vaccinated with a Medicines and Healthcare products Regulatory Agency (MHRA) approved COVID-19 vaccine in the UK and at least 14 days having passed since having received the recommended doses of that vaccine.

When identified as a contact, NHS Test and Trace contact individuals and check whether they are legally required to self-isolate. Even if they have no symptoms, contacts will be advised to have a PCR test as soon as possible. Guidance is also given on preventing the spread of COVID-19, which states for the 10 days following contact with the positive case, people may want to consider:

  • limiting close contact with people outside your household, especially in enclosed spaces
  • wearing a face covering in enclosed spaces and where you are unable to maintain social distancing
  • limiting contact with anyone who has an underlying health condition that puts them at higher risk of severe illness if infected with COVID-19
  • taking part in twice-weekly lateral flow testing

If a contact subsequently tests positive for COVID-19 they must follow the legal requirement to self-isolate.

Please note, the data in this bulletin was collected prior to the changes to self-isolation policy based on the Omicron variant. Changes to policy were introduced from 30 November 2021. More information can be found in Guidance for contacts of people with confirmed coronavirus (COVID-19) infection who do not live with the person. Please note this guidance is updated regularly.

Self-isolation

Self-isolation is when individuals do not leave their home because they have, or might have, COVID-19.

Statistical significance

The term "significant" refers to statistically significant changes or differences. Significance has been determined using the 95% confidence intervals, where instances of non-overlapping confidence intervals between estimates indicate the difference is unlikely to have arisen from random fluctuation. More information is available on our uncertainty web page.

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3. Measuring the data

Survey information

This is the second bulletin in this series, with the survey in its current format and using the current data collection methodology.

The COVID Test and Trace Contacts Behavioural Insights Study aims to understand the behaviour, attitudes and well-being of individuals identified as a contact of someone who has tested positive for coronavirus (COVID-19) and does not need to self-isolate because of being fully vaccinated. This survey was specifically designed in consultation with Office for National Statistics (ONS) experts to obtain information on this group of people.

Estimates for this survey

The data were collected between 22 and 27 November 2021. The sample was stratified to be representative of the age, sex and regional distribution of the fully vaccinated “contacts” population in England. The achieved sample consisted of 918 adults.

Percentages in this report are based on weighted counts that are representative of the population of adults (aged 18 years or over) who had received at least two doses of a COVID-19 vaccine and were notified as being in contact with someone who tested positive for COVID-19 between 25 October and 21 November 2021.

The survey was conducted via telephone and all answers were self-reported. Of those potential respondents who were successfully contacted by an interviewer, the response rate was 63.0%. When including cases where contact was attempted but not made, the response rate was 15.6%. As with all surveys, these estimates have an associated margin of error.

Respondents were randomly sampled through the Contact Tracing and Advice Service (CTAS) database, held by NHS Test and Trace. The sample was limited to those who were fully vaccinated, had provided a valid phone number and who had been entered onto the CTAS database at the point of sampling. A random sample was selected from a sample frame which included all contacts whose date of exposure was between 11 and 16 November 2021.

Strengths and limitations

The main strengths of the COVID Test and Trace Contacts Behavioural Insights Survey include:

  • timely production of data and statistics that can respond quickly to changing needs, as the questions included are reviewed for each survey wave
  • the sample was stratified to be representative of the age, sex and regional distribution of the population being sampled and percentages are based on weighted counts representative of the population
  • quality assurance procedures are undertaken throughout the analysis stages to minimise the risk of error
  • confidence intervals have been used to determine whether differences across time periods and groups are statistically significant

The main limitations of the COVID Test and Trace Contacts Behavioural Insights Survey include:

  • limited overall sample size because of the limited period in which fieldwork took place making it difficult to reach a large number of people
  • the behaviour during the 10 days following exposure to COVID-19 was self-reported and may be subject to recall bias, which influences how accurately respondents can recall past events and experiences; most interviews took place around 10 days following exposure to reduce this bias
  • the Experimental Statistics presented contain uncertainty; as with all survey data based on a sample, there is an element of uncertainty as they are susceptible to respondent error and bias
  • because of the nature of the target population, in which a large proportion of contacts are members of the same household, it is possible that the sample could include multiple members of the same household
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Manylion cyswllt ar gyfer y Bwletin ystadegol

Danielle Cornish and Hannah Mason
publicservicesanalysis@ons.gov.uk
Ffôn: +44 1633 456022