Out of the world's 135 million healthcare staff, up to 180,000 may have died from Covid-19 between January 2020 and May 2021, according to the UN health agency.

This grim estimate featured in a new World Health Organisation (WHO) paper based on the 3.45 million Covid-related deaths reported globally to the UN health agency up to May – a figure that the WHO said may well be at least 60 per cent lower than the actual number of victims.

WHO Director-General Tedros Adhanom Ghebreyesus said: "The backbone of every health system is its workforce. Covid-19 is a powerful demonstration of just how much we rely on these men and women, and how vulnerable we all are when the people who protect our health are themselves unprotected."

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More than 10 months since the first vaccines were approved, "the fact that millions of health workers still have not been vaccinated is an indictment on the countries and companies that control the global supply of vaccines," Tedros added.

"Data from 119 countries suggest that on average, two in five healthcare workers globally are fully vaccinated. But of course, that average masks huge differences across regions and economic groupings."

"In Africa, less than one in ten health workers have been fully vaccinated. Meanwhile, in most high-income countries, more than 80 per cent of health workers are fully vaccinated," the WHO chief said.

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Workers in clinics and hospitals have been on the pandemic's front lines since the first Covid-19 cases were detected in China's Wuhan in late 2019, and many are suffering from burnout, anxiety and fatigue as the virus continues to spread around the world.