The waning protection against infection offered by vaccines against Omicron also complicates the picture. Laboratory studies have indicated that inactivated-virus vaccines, which make up almost half of the 10 billion doses distributed worldwide, elicit few antibodies against the variant. Does that mean that Omicron will rip through places that rely on these shots even faster?

Not necessarily, says Woolhouse. “The inactivated-virus vaccines might induce a broader immunity that would react to a wider range of strains because it will elicit immune responses against viral proteins other than spike, which is particularly variable,” he says. “It’s a very interesting question but I simply haven’t seen a formal analysis of it yet.”

That’s because there is little real-world data to go on. “It’s only just hitting countries that have used them,” says Pagel.