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.
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.
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.’