WHO chief Tedros Adhanom Ghebreyesus said health care workers needed to be among the first immunised against the disease, as he slammed the global inequity in the vaccine roll-out.
"Data from 119 countries suggest that on average, two in five health and care workers globally are fully vaccinated. But of course, that average masks huge differences," he said.
"In Africa, less than in one in 10 health workers have been fully vaccinated. Meanwhile, in most high-income countries, more than 80 percent of health workers are fully vaccinated."
He added: "We call on all countries to ensure that all health and care workers in every country are prioritised for COVID-19 vaccines, alongside other at-risk groups."
'Duty of care'
Annette Kennedy, president of the International Council of Nurses, said the organisation grieved for all health care workers who had lost their lives in the pandemic - "many needlessly; many we could have saved".
"It's a shocking indictment of governments. It's a shocking indictment of their lack of duty of care to protect health care workers who have paid the ultimate sacrifice," she said.
Kennedy warned: "They are now burnt out, they are devastated, they are physically and mentally exhausted. And there is a prediction that 10 percent of them will leave within a very short time."
The WHO wants each country to have vaccinated 40 percent of its population by the end of the year, but Tedros said 82 countries are at risk of missing that target, chiefly through insufficient supply.
In high-income countries, as categorised by the World Bank, 133 doses have been administered per 100 people. In the 29 lowest-income nations, the figure drops to five.