Simon Clarke, an associate professor in cellular microbiology at the University of Reading, said that while both variants had some new features in common, the one found in South Africa “has a number additional mutations … which are concerning”.

He said these included more extensive alterations to a key part of the virus known as the spike protein – which the virus uses to infect human cells – and “may make the virus less susceptible to the immune response triggered by the vaccines”.

Lawrence Young, a virologist and professor of molecular oncology at Warwick University, also noted that the South African variant has “multiple spike mutations”.

“The accumulation of more spike mutations in the South African variant are more of a concern and could lead to some escape from immune protection,” he said.