World Health Organization (WHO) official David Nabarro has said that wealthy countries including the UK should send spare vaccine doses to virus-hit nations before organizing booster jabs .

WHO Special envoy Nabarro told the BBC top-ups and extra vaccinations “should come a bit later”.

He said Covid was “bigger than ever, it’s fiercer than ever and it’s causing more distress than ever” worldwide.

The UK has said its booster program could start as early as September. The government has also pledged to donate surplus vaccine doses to poorer nations.

But the WHO has urged richer countries to do more – and sooner – as Covid cases surge in countries, including India and South Asian nations.

Nabarro told BBC Radio 4’s World at One program the virus was now spreading in places where testing was poor – so the numbers being reported risk being a “major under-estimate”.

“This is a bad phase,” he said.

As foreign ministers of the G7 group of countries meet in London, he urged leaders to begin to distribute spare doses to those countries in the grip of the virus amid a global shortage of supply.

He said he wanted “to plead with G7 leaders, with G20 leaders, with every leader, with everybody who’s got influence, to please recognise that we’ve got to try to get vaccines distributed to those who need them the most now in this period of acute shortage of supply.”

Mr Nabarro added that “top-ups and other extra things and extra protection for people in the wealthy countries… should come a bit later.”