The pupil antibody test used in the COVID-19 Schools Infection Survey (SIS) is based on oral fluid collection as this is a non-invasive alternative to collecting blood but this test has a lower sensitivity (estimated at 80%); after adjusting for the sensitivity of the test, in Round 6 (14 June to 6 July 2021), 11.25% of primary school pupils and 12.95% of secondary school pupils in the local authorities sampled had antibody levels above the limit of detection.
The antibody conversion rate (testing positive after having tested negative in the previous round) between rounds 4 and 6 (March to July 2021) was the lowest seen between any two consecutive testing points in SIS at 2.3 per 1,000 person-weeks for primary school pupils and 1.4 per 1,000 person weeks for secondary pupils; there was no significant difference between conversion rates of primary school pupils and secondary school pupils.
A technical article has been released alongside this bulletin which provides further details on methods for estimating the proportion “ever testing” positive for SARS-CoV-2 antibodies over the course of SIS.
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In the case of the coronavirus (COVID-19), antibody conversion is defined when a positive antibody test result is recorded following a negative result in the previous testing round and will capture both symptomatic and asymptomatic infections that may have been missed between testing rounds.
To account for the different follow-up times between the rounds (on average the follow-up time between rounds 1 and 2 was three weeks, between rounds 2 and 4 was 15 weeks, and between rounds 4 and 6 was 13 weeks), the antibody conversion rate has been calculated and expressed per 1,000 person-weeks. More details on this methodology are available.
In some cases the confidence intervals around these estimates are wide because of the small number of participants who recorded antibody conversion and caution should be taken when interpreting results. When numbers are small, weighting the data can also mean that a small number of individuals have a large impact on the antibody conversion rate.
The antibody conversion rate in oral fluids has continued to decrease in rounds 4 to 6 (March to July 2021, 2.0 per 1,000 person-weeks) for all pupils combined. This compares to the highest rate which was between rounds 1 to 2 (November to December 2020, 12.0 per 1,000 person-weeks), and is also lower than the rate seen between rounds 2 to 4 (December 2020 to March 2021, 5.7 per 1,000 person-weeks).
The antibody conversion rate between rounds 4 and 6 was the lowest seen between any testing rounds. There was no significant difference between antibody conversion rates of primary school pupils (2.3 per 1,000 person-weeks) and secondary school pupils (1.4 per 1,000 person-weeks) between rounds 4 and 6.
More about coronavirus
COVID-19 Schools Infection Survey Round 6 pupil antibodies
Dataset | Released 27 October 2021
Initial estimates of pupils testing positive for SARS-CoV-2 antibodies from the COVID-19 Schools Infection Survey across a sample of schools, within selected local authority areas in England.
The Coronavirus (COVID-19) Schools Infection Survey analysis was produced by the Office for National Statistics (ONS) in collaboration with our research partners at the London School of Hygiene and Tropical Medicine and UK Health Security Agency.Back to table of contents
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. Overlapping confidence intervals indicate that there may not be a true difference between two estimates. For more information, see our methodology page on statistical uncertainty.
A result is said to be statistically significant if it is likely not caused by chance or the variable nature of the samples. For more information, see our methodology page on statistical uncertainty.
Antibody conversion rate
Please refer to the Glossary section of the COVID-19 Schools Infection Survey, Round 4, pupil antibody data bulletin.
Data presented in this bulletin are from Round 6 of the COVID-19 Schools Infection Survey (SIS). These findings are for SARS-CoV-2 antibodies for pupils only.
Estimates have been weighted and are representative of the ethnicity, gender, and age for all pupils in the sampled local authorities.
Our methodology article provides further information about response rates, survey design, how we process data and how data are analysed.
The results presented in this bulletin are from antibody tests conducted in schools in England between 14 June and 6 July 2021, referred to as Round 6.
Results have also been presented from tests conducted in schools in England between 3 and 20 November 2020 (referred to as Round 1), between 30 November and 11 December 2020 (referred to as Round 2), and between 15 and 31 March 2021 (referred to as Round 4).
Round 3 was due to take place in late January 2021. Testing within schools for this round was cancelled because of restricted attendance in schools during the national lockdown.
In Round 6, 141 schools took part in testing (57 primary and 84 secondary).
Before the beginning of Round 4, participation was offered to all year groups in secondary schools (excluding Year 11) to improve the sample size. Some 63 out of the 84 secondary schools that took part in Round 6 testing had extended participation to other year groups.
In Round 6 of testing, 12,485 pupils (4,243 primary and 8,242 secondary) took part in at least one current coronavirus (COVID-19) infection or COVID-19 antibody test. The estimated response rate for secondary school pupils, in the year groups that participation was offered to, was 17%. The estimated response rate for primary school pupils was 24%. Details of previous rounds response rates can be found in the accompanying dataset.
More quality and methodology information on strengths, limitations, appropriate uses, and how the data were created is available in our methodology article.
Data cleaning and quality assurance is being carried out on data collected as part of the study on an ongoing basis. All estimates presented in this bulletin are provisional results. Estimates may therefore be revised in future publications.Back to table of contents
Contact details for this Statistical bulletin
Telephone: +44 20 8039 0326