Experts remain divided over merits of mass Covid tests in schools

The education secretary, Gavin Williamson, has put mass testing for coronavirus at the heart of his strategy to reopen schools after the lockdown. It is a controversial strategy that has divided scientists. Some believe mass testing can help reduce outbreaks at schools, while others argue it could make matters worse by giving teachers and pupils false reassurance.

Mass testing relies on lateral flow tests, or LFTs, which contain antibodies that bind to the virus. When a nasal swab is tested in an LFT, any virus present in the sample sticks to the antibodies and produces a dark band, a bit like a pregnancy test’s indicator. LFTs are not as accurate as the standard NHS lab-based PCR tests, but they are cheap and produce results fast – within 30 minutes.

The downside of LFTs is their performance. In a pilot trial in Liverpool, mass testing failed to spot more than half the people who were infected but had no symptoms. The tests missed nearly a third of asymptomatic people who had high viral loads and were at highest risk of spreading the disease.