The WHO said earlier this month data did not indicate a need for booster shots, while topping up already fully vaccinated people would further increase vaccine inequity between rich and lower-income countries.

“A third dose of vaccine is not a luxury booster (that is) taken away from someone who is still waiting for a first jab. It’s basically a way to keep the most vulnerable safe,” Hans Kluge, head of WHO Europe, told a press briefing.

Kluge also said an increase in Covid-19 transmission rates across Europe over the last two weeks, combined with low levels of vaccination in some countries, were “deeply worrying”.