The director general of the World Health Organization (WHO) has revealed the disparity of global coronavirus vaccine distribution during a briefing on COVID-19 to international media.
Dr Tedros Adhanom Ghebreyesus said that in high-income countries, an average of almost one in four people has received a vaccine. In low-income countries, it is one in more than 500.
Ghebreyesus said: "There remains a shocking imbalance in the global distribution of vaccines.
"More than 700 million vaccine doses have been administered globally, but over 87% have gone to high income or upper middle-income countries, while low income countries have received just 0.2%.
"Let me repeat that: one in four versus one in 500."
At the start of 2021 the WHO called for vaccination programmes to begin in every country in the world within the first 100 days of the year.
Saturday 10 April will be day 100.
Ghebreyesus added: "Out of 220 countries and economies, 194 have now started vaccination, and 26 have not. Of those, 7 have received vaccines and could start, and a further 5 countries should receive their vaccines in the coming days.
"That leaves 14 countries who have not yet begun vaccination, for a range of reasons. Some have not requested vaccines through COVAX, some are not yet ready, and some plan to start in the coming weeks and months."
And the director general highlighted the need for governments to consider sharing their vaccine supplies, saying: "Most countries do not have anywhere near enough vaccines to cover all health workers, or all at-risk groups, never mind the rest of their populations.
"This is a time for partnership, not patronage.
"Scarcity of supply is driving vaccine nationalism and vaccine diplomacy."
Last week, India - the second most populated country in the world - launched its most ambitious vaccination programme yet, aiming to administer 400 million vaccines in order to curb the growing third wave of infections in the country.
However by Friday signs could be seen outside vaccination centres advising that supplies had run out.
Almost 32 million Britons have received their first dose of the coronavirus vaccine, with 6.5 million having received both doses.
The UK's vaccination programme is the largest of its kind ever seen in the country.
This week the safety of the Oxford/AstraZeneca jab was again called into question when the Joint Committee on Vaccination and Immunisation (JCVI) said people under 30 should be offered the Pfizer or Moderna jabs instead.
It followed an investigation by the Medicines and Healthcare products Regulatory Agency (MHRA), which found an "extremely small" number of blood clot cases – 79 – among more than 20 million AstraZeneca doses administered up to 31 March. There were 19 deaths.
Speaking at a televised briefing at the Department of Health on Wednesday, Dr June Raine, chief executive of the MHRA, made a point of reiterating: "This is extremely rare."
Questions have also been raised about whether receiving a COVID-19 vaccination could affect fertility, but England's deputy chief medical officer, Jonathan Van-Tam, dismissed the fears in during a Q&A with Sky News.
He said: "First of all it is just not biologically logical that they would. Secondly, no vaccine has ever done this.
"Getting COVID does affect your long-term chances of life and that's a pretty important counter-balance."
Watch: Do coronavirus vaccines affect fertility?