US biotech Moderna said its Covid-19 vaccine had shown 94.5 per cent efficacy in clinical trials, in the second positive set of results for a potential coronavirus shot in the past eight days. Last week, US pharmaceutical company Pfizer and Germany’s BioNTech also said their vaccine, which uses the same messenger RNA technology, was found to be more than 90 per cent effective. The Moderna finding, hot on the heels of that breakthrough, will further