MODERNA’S vaccine is causing a rash on some people’s arms after injection.The side effect, dubbed “Covid arm”, appears around a week after receiving a dose and affects very few patients, doctors say.But they stressed that people with the harmless reaction should still get their second dose of the jab for optimal protection against Covid - around 95 per cent for the Moderna jab.The Moderna vaccine is being dolled out in the US after authorisation in December, but is not expected in the UK until March.It uses the same mRNA technology as the Pfizer vaccine, which has been given to millions...