Australia, New Zealand and some Southeast Asian countries that have never had major outbreaks also face “a bumpy exit” because they have little natural immunity and, thus, “their only way of exiting is really close to 100% vaccination.”

Looming over all of this is the threat from variants.

“If you wanted to conduct an experiment of how to encourage this virus to go down a variant pathway, it would be to have … some countries with very high vaccine uptake, some with very low, some countries with a lot of natural immunity, some countries with little natural immunity,” Farrar says.

“We’re giving an evolutionary advantage to this virus, which I hope it doesn’t exploit.”