Covid-19 is believed to be deadlier than other strains in the UK, experts have warned.The Manaus P1 mutation is thought to possess a "double whammy" of being both more contagious and better at "evading antibodies" than the strain first discovered in Kent.Danny Altmann, professor of immunology at Imperial College, said it was "likely" the Brazilian variant was "breaking through" antibodies built up by previous infection.Referring to new research on the Brazilian city of Manaus, published in The Lancet, Professor Altmann also said urgent action was needed to prevent other strains being imported from abroad, but admitted the task was a "really, really hard challenge"."It was expected that there would be quite a high level of protection there.