We are grateful to Professor Chris Whitty (Chief Medical Officer) and his expert colleagues for their continued and constructive engagement with our work. We also recognise that the Government, following the advice of the Chief Medical Officer and others, has taken a considered approach to implementing the SIREN study. We note that the Government aims to utilise the SIREN study to better inform the frequency at which, and under what circumstances, the testing of NHS staff for coronavirus ought to take place.