New results from simulation-based assessment imply that regular, whole-school use of Covid-19 screening tests based on lateral flow devices, reduces the need for further closures after the 8th of March, but does not replace the need for symptomatic isolation of close contacts. 

During the Covid-19 outbreak, school closures have been used as part of governments’ non-pharmaceutical interventions to reduce the number of contacts and keep the reproduction number below 1. Prolonged school closures have a profound negative impact on the future opportunities of pupils, particularly those from disadvantaged backgrounds, as well as additional economic and social impacts by preventing parents from returning to work.

Data on Covid-19 in children are sparse and policy frameworks are evolving quickly. Researchers at the Medical Research Council (MRC) Biostatistics Unit (BSU) at the University of Cambridge have compared a set of potential policies to accompany the reopening of schools. The team, led by Professor Sylvia Richardson, used a newly developed realistic agent-based simulation prototype informed by available data.

A key point of interest is that a once-a-week use of screening tests based on lateral flow devices would help schools to remain open after the 8th of March. Policies were compared on their potential to contain new outbreaks of Covid-19 in schools, and on the proportion of school days lost due to isolation of pupils.

Isolation of symptomatic pupils and their closest contacts is England’s reference policy. In addition, regular asymptomatic screening of entire schools is beneficial across a wide range of scenarios. This conclusion about relative performance remains valid even when compliance with testing requirements is lower or the sensitivity of the employed test devices is lower than currently anticipated. Actual policy-performance is affected by both uptake and sensitivity.

Professor Sylvia Richardson, Director of the MRC Biostatistics Unit, University of Cambridge, said: “This agent-based simulation provides detailed understanding of the relative effectiveness of a range of school policies to guide public health authorities in choosing good candidates to be trialled and evaluated. Our prototype is flexible, it can be adapted to include new emerging data on transmission in children and adolescents, so that policies to keep schools open can evolve as the pandemic context unfolds.”

Professor Sheila Bird, former Programme Leader at the MRC Biostatistics Unit, University of Cambridge, added: “Our prototype assumed that a positive lateral flow test result for an index case leads to immediate isolation of, and return home of, the entire bubble of the index case. However, the bubble (and the index case) return to school after 2 days if the index case’s PCR turns out to be negative. PCR-adjudication is not happening in early March in England’s secondary schools.”

Full paper available: https://arxiv.org/abs/2103.02035 

Funding acknowledgements: This work was supported by the UK Medical Research Council programme and an Alan Turing Institute fellowship.

Contact for media enquiries: Alison Quenault – alison.quenault@mrc-bsu.cam.ac.uk