Daily testing for students exposed to COVID-19 may be equally as effective as isolation of contacts for controlling school transmission
23 July 2021
- Daily testing of students and staff who have been in contact with COVID-19, rather than isolating whole groups, may be just as effective in controlling transmission in secondary schools
- Findings indicated only a small percentage (1.5-1.6%) of students and staff tested positive for COVID-19 after close contact with a case in school or college
- This means that approximately 98% of contacts in the trial did not develop COVID-19 during the isolation period
- Rates of COVID-19 in school staff were lower than in students
A study by the University of Oxford has found that daily testing of secondary school students who were in contact with someone with COVID-19 was just as effective in controlling school transmission as the current 10-day contact isolation policy. The independent study, sponsored by the Department of Health and Social Care and supported by the Department for Education and Office for National Statistics, ran between April and June 2021. The results were published today in pre-print.
201 secondary schools and colleges of further education were randomised into two groups. Over 200,000 students and 20,000 staff participated. Half of the schools continued a standard policy of routine mass testing, and isolation for close contacts of positive cases for 10 days. The second group of schools invited close contacts of positive cases to come to school and take lateral flow tests in a supervised school testing site over 7 days. Those who chose to do so were released from isolation to attend school or college if they tested negative for COVID-19. Around half of all eligible students and staff chose to do daily testing. Close contacts, from either group of the study, were invited to provide a research PCR test for COVID-19 on day 2 and 7 following contact, in order to determine how many close contacts became infected.
The research PCRs used in the study showed that 44/2981 (1.5%) of the contacts attending school in the intervention group tested positive or indeterminate for COVID-19, compared to 14/886 (1.6%) of the control students and staff staying at home.
There was no evidence that the rate of students and staff developing COVID-19 with symptoms was different in the group doing daily testing compared to the contact group isolating at home. As with all studies we determined a range of plausible values for the impact of the intervention. At the rates of COVID-19 seen during the study, we found that daily contact testing may reduce the rate of COVID-19 cases in schools by around 1 cases a month per school of 1000 students, to a maximum possible increase of transmission by 1 cases per month in a school of 1000 students. However, the most likely outcome was that there would be no overall change.
In the control group, 1.8% of available student school days were lost due to COVID-19, some of which were due to contacts outside of school. As expected, daily testing, rather than isolation of contacts, can reduce absences. Where school-based contacts take part in DCT, the best estimate was that this can reduce COVID-related school absences by 39%.
Tim Peto, Professor of Medicine at the University of Oxford and Principal Investigator on the study, says: ‘Our findings indicate that there is no significant difference in COVID-19 transmission between schools where bubbles were sent into home isolation versus those where daily contact testing was implemented instead. Infection rates in the close contacts were low in general, and there was little difference between those who went to school following a negative lateral flow test and those who were isolating at home.’
Bernadette Young, Clinical Lecturer in Infectious Diseases at the University of Oxford, and an investigator on the study says: ‘When DCT is used in schools, our best estimate is that transmission is slightly reduced compared to a policy of isolating contacts, though there is uncertainty around this. We are now doing whole genome sequencing of the viruses to understand whether cases in the study were related to each other, which will help us understand transmission in secondary schools and colleges.’
David Eyre, Associate Professor at the University of Oxford, and an investigator on the study says: ‘The findings of this study are good news for students, parents and teachers. The study supports earlier findings from Test and Trace data showing that most children who are in contact with COVID-19 in schools don’t go on to get infected. Daily testing was able to identify most of the small number that do, which allowed them to safely isolate at home, while allowing the large majority of other students and staff to remain in school. Reassuringly too, rates of infection in school staff were lower than those in students.’
Susan Hopkins, Chief Medical Adviser for NHS Test and Trace says: ‘This is a major breakthrough, showing that daily contact testing can keep young people in classrooms instead of making them isolate at home. Children and parents have made enormous personal sacrifices throughout this pandemic by isolating when needed, and we all know the disruption it has caused in their lives.
‘We’ve been trying to find safe alternatives, and this study gives us evidence of safe alternatives to isolation for school contacts. So far, self-isolation has been one of the most effective tools at our disposal against COVID-19 – stopping isolated cases from becoming major outbreaks. To have another potential tool like this is great news.
‘Trailblazing studies like this are only possible because of the collective efforts of the scientific community and the participation of huge numbers of schools and colleges, parents and teachers, and we are hugely grateful and want to thank every person and organisation that has made this research possible.’
Sir Ian Diamond, National Statistician, Office for National Statistics says: ‘Throughout the pandemic we have worked closely and effectively with our excellent study partners to deliver a highly successful COVID – 19 surveillance programme.
‘This latest research is vital to our understanding of close contact with positive cases in schools. This information will remain an important part of our study programme, alongside the continued monitoring of infections and antibodies in the general population.
‘Once again we thank everyone taking part in all of these studies. We will continue to depend on your involvement to help us find the safest way back to complete normality.’
Notes to editors
For further information and interview requests, contact:
- Gen Juillet, Media Relations Manager, University of Oxford, firstname.lastname@example.org
- Alexander Buxton, Head of Strategic Communications (Research & Innovation), University of Oxford, email@example.com
Full pre-print: http://modmedmicro.nsms.ox.ac.uk/wp-content/uploads/2021/07/dct_schools_trial_preprint_20210722.pdf
For further information, here is a qualitative report on the DCT study in schools, completed by the University of Bristol: http://www.hprubse.nihr.ac.uk/EasysiteWeb/getresource.axd?AssetID=90034&servicetype=Attachment
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