The chief executive of Moderna has predicted that existing vaccines will be much less effective at tackling Omicron than earlier strains of Covid-19 and warned it would take months before pharmaceutical companies can manufacture new variant-specific jabs at scale.

The high number of Omicron mutations on the spike protein, which the virus uses to infect human cells, and the rapid spread of the variant in South Africa, suggested the current crop of vaccines may need to be modified next year.

There is no world, I think, where [the effectiveness] is the same level . . . we had with Delta.

I think it’s going to be a material drop. I just don’t know how much because we need to wait for the data. But all the scientists I’ve talked to . . . are like ‘this is not going to be good’