COVID-19 Schools Infection Survey Round 4, England: March 2021

• Round 4 of the study took place from 15 to 31 March 2021 shortly after schools in England reopened following the third COVID-19 lockdown; results suggest that current infection was lower amongst staff and pupils in secondary schools compared with results from the study collected in November and December 2020.

• In Round 4, 0.34% of secondary school pupils tested positive for current infection (95% confidence interval: 0.16% to 0.63%) compared with 0.19% of secondary school staff (95% confidence interval: 0.04% to 0.58%) across schools from 14 local authorities taking part in the study.

• When using comparable data, the percentage of secondary school pupils testing positive for current infection was significantly lower than Round 1 and lower than Round 2 (but with overlapping confidence intervals), 0.33% compared with 1.42% and 1.22% respectively.

• When using comparable data, the percentage of secondary school staff testing positive for current infection was significantly lower than that seen in Round 1 and Round 2 (0.32% compared with 1.36% and 1.64% respectively).

• In Round 4, the number of positive test results for primary schools is too small to present because of statistical disclosure criteria.

• 137 schools (57 primary, 80 secondary) in 15 local authorities participated in the fourth round of testing; within these schools, 15,187 participants (4,154 staff and 11,033 pupils) had at least one test in Round 4.

Figure 1 shows the percentage of secondary school pupils and staff testing positive for current coronavirus (COVID-19) infection in Round 4 (15 to 31 March 2021). 0.34% of secondary school pupils tested positive (95% confidence interval: 0.16% to 0.63%) compared with 0.19% of secondary school staff (95% confidence interval: 0.04% to 0.58%).

The number of positive test results in Round 4 from primary school pupils and staff is too small to present because of statistical disclosure criteria.

For comparison between rounds, we have used data from the 11 local authorities with at least two primary and two secondary schools participating in all testing rounds. These are not necessarily the same schools or participants tested between the rounds.

The percentage testing positive for current COVID-19 infection in Round 4 was lower than in previous rounds; this can be seen in Figure 2 for secondary school staff and pupils. In Round 4, 0.33% of secondary school pupils tested positive (95% confidence interval: 0.13% to 0.67%), this was significantly lower than Round 1 (1.42%, 95% confidence interval: 0.69% to 2.59%).

For secondary school staff, 0.32% tested positive in Round 4 (95% confidence interval: 0.10% to 0.76%). This is significantly lower than both previous rounds; Round 1: 1.36% (95% confidence interval: 0.85% to 2.07%) and Round 2: 1.64% (95% confidence interval: 1.10% to 2.33%).

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 Public Health England.

Data presented in this bulletin are from Round 4 (with comparisons with Round 1 and Round 2) of the COVID-19 Schools Infection Survey (SIS), which looks to identify the percentage of pupils and staff testing positive for the (COVID-19). These findings are from testing for current infection for coronavirus (COVID-19) only. Antibody data will follow in a bulletin to be published on 27 May 2021.

For more information on the survey data and response rates from previous rounds please see our previous bulletins. Our methodology article provides further information about survey design, how we process data and how data are analysed.

Reference period

The results presented in this bulletin are from virus swab tests conducted in schools in England between 15 and 31 March 2021 - referred to as Round 4. Testing for current infection in SIS is carried out using nasal swab (PCR) tests. This study is independent to the rapid asymptomatic testing introduced in schools using lateral flow devices (LFD).

Results have also been presented from tests conducted in schools in England between 3 and 19 November 2020 - referred to as Round 1, and between 2 and 10 December 2020 - referred to as Round 2.

Round 3 was due to take place in late January 2021. Testing within schools for this round was cancelled because of schools in England being shut to the majority of pupils during lockdown.

Response rates

As at 16 April 2021, in Round 4 of testing, 4,154 staff participated in at least one current COVID-19 infection or COVID-19 antibody test. This is around 35% of eligible staff in the sampled schools.

Prior to the commencement of Round 4, participation was offered to all year groups in secondary schools (excluding year 11) to improve the sample size. 42 out of the 80 secondary schools which took part in Round 4 testing had extended participation to other year groups. In Round 4 of testing, 11,033 pupils (3,762 primary and 7,271 secondary) participated in at least one current 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 20%.

Details of previous rounds response rates can be found in the accompanying dataset.

Quality

Further 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.