Just hours after US President Joe Biden vowed to supercharge the battle against the coronavirus with a donation of 500 million Pfizer shots, Johnson said Britain would give at least 100 million surplus vaccines to the poorest nations.
Johnson has already called on G7 leaders to commit to vaccinate the entire world by the end of 2022 and the group is expected to pledge 1 billion doses during its three-day summit in the English seaside resort of Carbis Bay.
Some campaign groups condemned the plan as a drop in the ocean, with Oxfam estimating that nearly 4 billion people will depend for vaccines on COVAX, the program that distributes COVID-19 shots to low and middle income countries.
"As a result of the success of the UK's vaccine program we are now in a position to share some of our surplus doses with those who need them," Johnson will say on Friday, according to excerpts of the announcement released by his office.
"In doing so we will take a massive step towards beating this pandemic for good."
COVID-19 has killed around 3.9 million people and ripped through the global economy, with infections reported in more than 210 countries and territories since the first cases were identified in China in December 2019.
G7 leaders meeting in Britain will also endorse US President Joe Biden's proposal for global minimum tax of at least 15% on corporations, White House national security adviser Jake Sullivan said on Twitter on Friday.
The US Treasury in May proposed a global minimum corporate tax of at least 15% to try to end a downward spiral of corporate tax rates and deter multinational companies from shifting profits to tax-haven countries.
GLOBAL EFFORT
While scientists have brought vaccines to market at breakneck speeds - Britain has given a first dose to 77% of its adult population and the United States 64% - they say the pandemic will only end once all countries have been vaccinated.
With a global population nearing 8 billion and most people needing two doses, if not booster shots to tackle variants as well, campaigners said the commitments marked a start but that world leaders needed to go much further, and much faster.
"If the best G7 leaders can manage is to donate 1 billion vaccine doses then this summit will have been a failure," Oxfam's health policy manager Anna Marriott said, adding that the world would need 11 billion doses to end the pandemic.
Oxfam also called on G7 leaders to support a waiver on the intellectual property behind the vaccines.
"The lives of millions of people in developing countries should never be dependent on the goodwill of rich nations and profit-hungry pharmaceutical corporations," Marriott said.
Of the 100 million British shots, 80 million will go to the COVAX program led by the World Health Organization (WHO) and the rest will be shared bilaterally with countries in need.
Johnson echoed Biden in calling on his fellow leaders to make similar pledges and for pharmaceutical companies to adopt the Oxford-AstraZeneca model of providing vaccines at cost for the duration of the pandemic.
Leaving poorer countries to deal with the pandemic alone risks allowing the virus to further mutate and evade vaccines. Charities have also said that logistical support will be needed to help administer large numbers of vaccines in poorer countries.
The British doses will be drawn from the stock it has already procured for its domestic program, and will come from suppliers Oxford-AstraZeneca, Pfizer-BioNTech, Janssen, Moderna and others.
Other pledges so far:
US drug-maker Pfizer and its German partner, BioNTech , will provide 200 million doses in 2021 and 300 million doses in the first half of 2022, which the United States will then distribute to 92 lower-income countries and the African Union.
EUROPEAN UNION, GERMANY, FRANCE, ITALY
European Commission President Ursula von der Leyen has said the European Union aims to donate at least 100 million COVID-19 vaccine doses to low- and middle-income countries by the end of 2021.
That includes a pledge by France and Germany to donate 30 million doses each, with Italy donating 15 million doses.
France has also said it has donated 184,000 doses of AstraZeneca's COVID-19 vaccine to Senegal through the COVAX vaccine-sharing program.
JAPAN
Japan has said it will donate about 30 million doses of vaccines produced within the country through COVAX.
Last week, Japan delivered to Taiwan 1.24 million doses of AstraZeneca's vaccine for free.
CANADA
Reuters has reported that Canada is in talks to donate excess doses through COVAX, although it has not yet made public any firm commitment of donations, or said how much it plans to donate.
GLOBAL CONTEXT
COVAX, backed by the World Health Organization (WHO) and the Global Alliance for Vaccines and Immunization (GAVI), aims to secure 2 billion vaccine doses for lower-income countries by the end of 2021.
WHO Director-General Tedros Adhanom Ghebreyesus has said the pandemic is being perpetuated by a "scandalous inequity" in vaccine distribution.
Before the new pledges this week, some 150 million doses had been pledged to COVAX, far short of the 250 million needed by the end of September, and a target of 1 billion by year-end.
Over 2.2 billion doses of COVID-19 vaccine have been administered worldwide, and around 560 million of those have been given in G7 countries alone.
The global population is estimated at around 7.8 billion people, about a quarter of whom are younger than 15. Most approved COVID-19 vaccines are two-dose shots.