The Moderna coronavirus vaccine has been approved for use in the UK. The jab is the third to be given the green light by the Medicines and Healthcare products Regulatory Agency (MHRA), along with the Covid-19 vaccines from Pfizer/BioNTech and Oxford/AstraZeneca. But unlike the previous jabs, the Moderna vaccine will not be available for use straight away, with the first doses not expected to arrive until the spring.