Asymptomatic screening for COVID-19 helps control transmission
During autumn term 2020, 12,781 students living in College accommodation participated in the University’s Asymptomatic COVID-19 Screening Programme. Students were initially screened every fortnight, but by week seven all participating students were offered screening every week. More than four out of five (82%) of all eligible students ultimately agreed to take part.
Participating students swabbed their noses and throats, then pooled their swabs in the same sample tube as other students from the same household. Pooled samples were analysed at the Cambridge COVID-19 Testing Centre, a collaboration between the University, AstraZeneca and Charles River Laboratories. Pooling swabs made the programme much more efficient, without losing test sensitivity. Over the study period, 50,376 swabs were screened, using only 16,945 tests.
There was no evidence that relying on voluntary participation, or using nose and throat swabs, was a barrier to students taking part. In fact, in a separate survey of more than 750 participants, over 95% of respondents were satisfied with the screening programme and thought that it had made an overall positive contribution to the Cambridge community.
Among 671 students diagnosed with SARS-CoV-2 infection over the study period (5% of participants), 299 (45%) were either identified or pre-emptively asked to self-isolate because of the screening programme. Using a model based on transmission at the University, the researchers estimated that weekly screening reduced the ‘R number’ – the average number of people an individual would infect in a susceptible population – by about a third.
Dr Nicholas Matheson, from the Cambridge Institute of Therapeutic Immunology and Infectious Disease (CITIID), designed the screening programme. He said: “By combining regular asymptomatic screening with readily accessible symptomatic testing, we were able to detect almost all cases of SARS-CoV-2 infection amongst students living in our Colleges.
“We hope our screening programme will serve as a useful example for other universities and colleges looking at ways to keep their students, staff and communities safe. We’ve shown that it’s possible to do this at scale by pooling samples, making it logistically and economically viable, without compromising test performance.
“Most importantly, we’ve provided real-world evidence that regular, voluntary asymptomatic screening can be effective in helping control COVID-19 transmission. With the current uncertainty around new variants of concern, and most young adults in the UK – let alone the world – not yet vaccinated, that’s an important lesson about mass testing in general, not just in universities.”