"This G7 is meeting as the pandemic still rages, vaccine justice has to be at the top of the agenda," said Kirsty Mcneill of Save The Children charity.
Johnson said he expected G7 leaders to agree the donations as part of a plan to inoculate the world's nearly 8 billion people against the coronavirus by the end of next year.
After Biden vowed to supercharge the battle against the virus with a donation of 500 million Pfizer shots, Johnson said Britain would give at least 100 million vaccines within the next year. Other pledges may follow.
But health and anti-poverty campaigners said that while the donations were a step in the right direction, Western leaders had shown a lack of ambition and a failure to grasp the exceptional efforts needed to beat the virus.