About 3.5 million people have lost their lives to COVID-19 this year, which is more than from HIV, malaria and tuberculosis combined in 2020, the World Health Organization said on Wednesday.

In the final WHO media briefing of the year, Tedros Adhanom Ghebreyesus, director general of the WHO, said that while science has delivered hope in the form of vaccines that saved lives this year, the inequitable sharing of vaccines has cost many lives.

Around 50 thousand people are still dying every week from the disease, Tedros said on Wednesday.

The WHO chief said while some countries are now rolling out blanket booster programmes, only half of the WHO's member states have been able to reach the target of vaccinating 40 percent of their populations by the end of the year, because of distortions in global supply.

"It's frankly difficult to understand how a year since the first vaccines were administered, 3 in 4 health workers in Africa remain unvaccinated," he said. "Enough vaccines were administered globally this year, (s0) that the 40 percent target could have been reached in every country by September, if those vaccines had been distributed equitably, through COVAX and AVAT."

However, he said there are encouraging signs that supply is improving, with COVAX, a facility co-led by the WHO that focuses on proportional allocation of doses among its 140-plus beneficiary states in accordance with population size, shipping its 800 millionth vaccine dose on Wednesday. Half of those doses have been shipped in the past three months.

"Our projections show that supply should be sufficient to vaccinate the entire global adult population, and to give boosters to high-risk populations, by the first quarter of 2022," Tedros said. "However, only later in 2022 will supply be sufficient for extensive use of boosters in all adults."

He stressed that blanket booster programs are likely to prolong the pandemic, rather than ending it, "by diverting supply to countries that already have high levels of vaccination coverage, giving the virus more opportunity to spread and mutate".

Tedros said: "It's important to remember that the vast majority of hospitalizations and deaths are in unvaccinated people, not un-boosted people."

The WHO wants all countries to reach the 40 percent target as quickly as possible, and the 70 percent target by the middle of next year.

"No country can boost its way out of the pandemic," he said. "And boosters cannot be seen as a ticket to go ahead with planned celebrations, without the need for other precautions."