Dr Clare Craig

Matt Hancock has announced a £100 billion spending programme for mass population testing — his so-called ‘moonshot' initiative, that would see 10 million tests delivered a day. Does this mean we need rocket boosters under the testing programme, fuelled by vast reserves of taxpayer cash? Thankfully, there could be a simpler and more pragmatic approach that not only saves money but would prevent a lot of harm. There are currently two main problems. The first is a poor definition of what constitutes a case of coronavirus. The second is a testing strategy designed for the wrong point in the pandemic. The government advisory group SAGE estimates that the standard tests used now have a false-positive rate of less than one per cent. But that's quite a big range.

Imagine a world where Covid-19 has been eliminated. To be certain this is true, the government conducts regular tests at random. The number of positive results should be zero, right? Wrong. There will always be a proportion of cases tested that come back with a false positive test result. Thankfully, for Covid-19, the false positive rate is less than one per cent of tests done. But it is not zero. It will be impossible for us to ever reach zero. Why? Because Covid-19 cannot be eliminated, even if it is likely to evolve to be more benign and become a seasonal problem like influenza.  Coronaviruses are, after all, seasonal, and as winter approaches we can expect more outbreaks of genuine Covid-19.