The vaccine miracle: how scientists waged the battle against Covid-19

In the early afternoon of 3 January this year, a small metal box was delivered to the Shanghai Public Health Clinical Centre addressed to virus expert Prof Zhang Yongzhen. Inside, packed in dry ice, were swabs from a patient who was suffering from a novel, occasionally fatal respiratory illness that was sweeping the city of Wuhan. Exactly what was causing terrifying rises in case numbers, medical authorities wanted to know? And how was the disease being spread?

Zhang and his colleagues set to work. For the next 48 hours, virtually non-stop, he and his team used advanced sequencing machines to unravel the RNA – the genetic building blocks – of the virus which they believed was responsible for the outbreak. Decoding the 28,000 letters of this RNA – which acts as letters of DNA do in a human – would give a precise indication of the new pathogen’s nature and behaviour.

And in the early hours of 5 January, Zhang and his team completed their task. The virus, they discovered, was a previously unknown coronavirus that was most closely related to one that had caused fatal outbreaks of severe