"The development of a coronavirus vaccine in approximately 300 days was a huge and unprecedented global achievement", said the British government in a statement ahead of a G7 video summit on Friday.
Mr Macron warned on Thursday that poorer countries were having to pay "astronomical prices" for western vaccines or resort to using the Chinese and Russian jabs, neither of which have been approved for use by regulators in Europe. But there remain more than 100 poorer countries where not a single dose has been given.
The British prime minister will on Friday chair the first G7 leaders' meeting during the U.K.'s presidency of the group of advanced economies.
The analysis found that, along with other Covid-19 vaccine supplies procured by the global Covax vaccine-sharing plan and in bilateral deals, the excess rich-country doses would go a long way to protecting vulnerable people in poorer countries.
The French president has called on the USA and Europe to back his proposal to share 4% to 5% of their coronavirus vaccine supplies, and in an interview with the Financial Times, said that German Chancellor Angela Merkel supports the idea.
USA officials, speaking to journalists on condition of anonymity ahead of the call, said that President Joe Biden would announce a total of $4 billion in funding for COVAX but that the country did not plan to share any of its doses with other nations until its domestic vaccination needs were met.
Coronavirus vaccines developed previous year required about 300 days of work, but Johnson wants this time to be reduced to 100 days, as recommended by the Coalition for Epidemic Preparedness Innovations (CEPI). However, the volume of surplus will depend on the vaccine supply chain and whether booster shots are needed in the autumn.