GENEVA/ZURICH: More producers of COVID-19 vaccines should follow the example of AstraZeneca and license their technology to other manufacturers, the head of the World Health Organization (WHO) said on Monday, as he described vaccine inequity as "grotesque".

WHO Director-General Tedros Adhanom Ghebreyesus noted that the drugmaker said earlier that interim data from trials found the vaccine, developed in conjunction with Oxford University, was 79% effective in preventing symptomatic COVID-19 and, crucially, posed no increased risk of blood clots.

"This data is further evidence that the AstraZeneca vaccine is safe and effective," Tedros told a news conference. WHO chief scientist Soumya Swaminathan called it a "very good vaccine for all age groups".

WHO officials said that there was no sign of falling demand for the AstraZeneca shot through its COVAX vaccine-sharing programme after some countries temporarily paused its use over health concerns.

"They did ask a lot of questions but the demand for the vaccine is extremely high," said WHO senior adviser Bruce Aylward. He added, however, that COVAX was having some "teething problems" since manufacturers might not be able to keep up with their roll-out programme.

The Geneva-based body urged vigilance as case numbers rise in several regions, including Europe, driven partly by virus variants that transmit more easily.

"Many countries are coming out of restrictive measures without good surveillance, without good vaccine coverage and a huge amount of fatigue at play," said WHO emergencies chief Mike Ryan, calling that "a recipe for larger outbreaks".