Masks

The ‘Danmask-19 trial' sought to test whether face masks are effective in preventing infection with SARS-CoV-2 (the virus that causes Covid-19) for the wearer. It found that the recommendation to wear surgical masks to supplement other public health measures 'did not reduce the SARS-CoV-2 infection rate among wearers by more than half in a community'. So does this mean wearing masks is a waste of time? There are several reasons that drawing such a conclusion from this study might be unwise. A randomised controlled trial (RCT) is often – though not always – the best way of testing whether a treatment works, because RCTs guard against the biases inherent in many other research designs.

Wind worries Sir: You are right to side with the 2013 version of Boris Johnson, when he claimed that wind power could not pull the skin off a rice pudding (‘Boris’s second wind’, 10 October). However, it was wrong to claim that offshore wind at £40 per megawatt hour makes Hinkley Point C, at over twice that price, look like a bad deal. The nuclear plant will be able to provide reliable, constant baseload power for up to 50 years. A wind plant will provide power only when the wind is blowing (and not blowing too hard). To provide reliable baseload requires fossil-fuelled backup. Second, the £40 per megawatt hour is the current strike price offered by the winners of projects to build new capacity.