GENEVA • Despite Covid-19 vaccines being rolled out in a number of countries, the World Health Organisation (WHO) warned on Monday that herd immunity would not be achieved this year.

Countries across the globe are looking forward to vaccines finally allowing a return to normality in the months ahead.

But the WHO's chief scientist Soumya Swaminathan warned that it will take time to produce and administer enough doses to halt the spread of the virus.

"We are not going to achieve any levels of population immunity or herd immunity in 2021," she told a virtual press briefing from the WHO's headquarters in Geneva on Monday, stressing the need to continue measures like physical distancing, hand washing and mask wearing to rein in the pandemic.

The coronavirus was first reported in the central Chinese city of Wuhan in late 2019 and has since spread around the world, infecting more than 90.5 million people and killing nearly two million.

Dr Swaminathan hailed the "incredible progress" made by scientists who managed the unthinkable of developing not one but several safe and effective vaccines against a brand new virus in under a year.

But, she stressed, the roll-out "does take time".

"It takes time to scale the production of doses, not just in the millions, but here we are talking about in the billions," she pointed out, calling on people to "be a little bit patient".

Dr Swaminathan stressed that eventually, "the vaccines are going to come. They are going to go to all countries". "But meanwhile we mustn't forget that there are measures that work," she said.

There would be a need to continue with the public health and social measures aimed at halting transmission for "the rest of this year at least".

Meanwhile, the head of the World Travel and Tourism Council said requiring Covid-19 vaccinations for international travel is akin to workplace discrimination and should be rejected.

"We should never require the vaccination to get a job or to travel," said the industry body's chief executive, Ms Gloria Guevara, who was speaking on a Reuters Next conference panel on Monday.

Some policymakers have suggested immunisation should be necessary for air travel. Qantas Airways has said it plans to introduce such a requirement.

"I totally disagree with the approach from Qantas," said Ms Guevara, whose organisation represents a sector accounting for as much as 10 per cent of global employment.

"If you require the vaccination before travel, that takes us to discrimination."

Airline safety protocols and on-board air filtration meant passengers had "less chance to get Covid in a plane (than) in a supermarket", she added.

"We need to protect vulnerable groups and prioritise the vaccination for them."

Ms Guevara's comments contrasted with the opinions of a majority of online panel viewers, who supported a vaccine requirement, according to a snap poll by conference organisers.

But she drew support from Air-Asia Group chief executive officer Tony Fernandes, who said global testing protocols remained key to unlocking travel.

Mr Fernandes said he was nonetheless "pessimistic" about countries' readiness to accept one another's tests and certificates, with many Asian states also likely to require vaccinations.

"There's a massive lack of trust out there right now," he said.

"Countries will say, 'Is that PCR (polymerase chain reaction) test really done to our standards?' Governments are becoming incredibly nationalistic."

AGENCE FRANCE-PRESSE, REUTERS