The first trial on humans of a vaccine against the coronavirus that causes Covid-19 has begun in Seattle. However, it will take at least 12 months to establish whether the jab – or any of the others being investigated around the world – is effective and safe. The publicly funded trial, which involves four volunteers, is of a vaccine which, unlike most, has not been produced from a weakened or inactivated virus. Instead, it contains a segment of genetic code copied from the virus: scientists hope this harmless strand will prime the human body to fight off the virus. Separately, reports that President Trump had offered a German firm, CureVac, a sum in the region of $1bn for exclusive rights to a Covid-19 vaccine it is working on sparked anger in Berlin. The company has categorically denied that such a request was ever made, but the reports intensified concerns that the long-standing transatlantic alliance has crumbled.