Campaigners have called on leaders at this week's G7 health summit in the United Kingdom to take concrete steps toward reducing the massive discrepancy in vaccine coverage between rich and poor countries.

Health ministers from the group of major economies, which includes the UK, Canada, France, Germany, Italy, Japan, and the United States, met at Oxford University on Thursday and Friday to discuss the COVID-19 pandemic, and improvements to global health.

The UK assumed the presidency of the group this year, and in the run-up to this week's meetings, Health Secretary Matt Hancock defended the G7's "strong track record" in supporting vulnerable populations. UK Foreign Secretary Dominic Raab said that G7 countries have committed to supporting the COVAX vaccine aid program and delivered COVID-19 vaccines to 127 countries and territories so far.

But campaign groups have noted that vaccine coverage in the developing world lags significantly behind nations like the US and the UK, which have both supplied first doses to more than half of their populations.

As of late May, globally, around 1.8 billion vaccines had been administered, according to Our World In Data. People living in G7 countries have received 497 million of these vaccines, or 28 percent, across a combined population of 775 million. People living in countries classed as low-income have received 5.5 million vaccines, or 0.3 percent, across a combined population of 660 million.

As well as inequitable distribution, vaccine hoarding has contributed to what the joint United Nations program on HIV/AIDS, known as UNAIDS has dubbed a "vaccine apartheid" between rich and poor countries.

Canada, for example, has procured enough treatments to vaccinate all its citizens 10 times, while the UK could theoretically vaccinate its entire population eight times.

"More than a million people have died from COVID since G7 leaders last met in February, when they made vague pledges to increase the global vaccine supply, but crucially failed to collectively back the waiver of intellectual property rules and investment in manufacturing vaccines in developing countries that would really make the difference," charity confederation Oxfam said in a statement.

Oxfam said that while some G7 members claim to have "done their bit" by pledging doses to COVAX, the initiative is "massively failing".

COVAX had hoped to ship 252 million COVID-19 vaccines in the first half of this year, although as of this week, just 77 million shots have been distributed. The World Health Organization noted that two recently-approved China-made vaccines could help buoy the flagging initiative.

Anna Marriott, Oxfam's Health Policy Manager, said that at present, developing nations cannot depend on COVAX or the "good will" of pharmaceutical companies, and that G7 ministers must expand measures to ensure vaccine rates increase in poorer countries.