The head of the European Medicines Agency told AFP on Friday that all countries must have access to coronavirus vaccines, as G7 leaders were expected to pledge to donate one billion doses to poor nations.

Emer Cooke also said in an interview that while the Amsterdam-based watchdog was confident current vaccines were effective against all different variants, that could "change quickly".

The comments by Ireland's Cooke -- who took over at the EMA late last year as it plunged into the scramble for a Covid vaccine -- came as G7 leaders met in Britain to discuss how to recover from the pandemic.

"This is not within the competence of the EMA so I can only speak from a personal perspective, where I really believe we need to ensure access, availability and access throughout the world, not just in the countries that have the means to pay for them," Cooke said.

Campaigners say the G7's vaccine donations pledge for this year and next -- including 500 million US doses -- is far too little, too late to end a pandemic that has claimed over 3.7 million lives worldwide and is still spawning new variants.

Despite a slow start, the EU has become one of the world's better protected regions, thanks to a stable of four vaccines approved by the EMA since December -- Pfizer/BioNTech, Moderna, AstraZeneca and Johnson & Johnson.

"To be honest, I thought we would be much further behind. The fact that we have four vaccines authorised within 15 months of the declaration of a pandemic is exceptional," said Cooke, speaking via Zoom.

But the emergence of new variants has however presented a new challenge, particularly the Delta variant which first emerged in India.

"So far we're confident that the circulating variants are controlled by the vaccines. But it can change very quickly," Cooke said.

The EMA has been working with vaccine makers to make sure they could adapt their jabs if needed, she said.