In an interview with the Los Angeles Times on Friday, Ms Harris said: “We didn’t see Delta coming. I think most scientists did not — upon whose advice and direction we have relied — didn’t see Delta coming.”

“We didn’t see Omicron coming. And that’s the nature of what this, this awful virus has been, which as it turns out, has mutations and variants,” she added.

Her comments come a day after Joe Biden warned of a “winter of severe illness and death” to the unvaccinated in his stark remarks after a meeting with his members of Covid-19 response team.