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

Stéphane Bancel said 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 that 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 [the] Delta [variant],” Bancel told the Financial Times in an interview at the company’s headquarters in Cambridge, Massachusetts.

He added: “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’. ”

The Moderna chief executive’s comments come as public health experts and politicians have tried to strike a more upbeat tone about existing vaccines’ capacity to confer protection against Omicron.

On Monday, Scott Gottlieb, a director of Pfizer and former commissioner of the US Food and Drug Administration, told CNBC: “There’s a reasonable degree of confidence in vaccine circles that [with] at least three doses . . . the patient is going to have fairly good protection against this variant.”

Joe Biden, US president, subsequently said Omicron was “a cause for concern, not a cause for panic,” adding that the government’s medical experts “believe that the vaccines will continue to provide a degree of protection against severe disease”.

However, Bancel said scientists were worried because 32 of the 50 mutations in the Omicron variant are on the spike protein, which current vaccines focus on to boost the human body’s immune system to combat Covid.