GENEVA (AFP) - Despite vaccines against Covid-19 being rolled out in a number of countries, the World Health Organisation warned Monday (Jan 11) 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 WHO's headquarters in Geneva, stressing the need to continue measures like physical distancing, hand washing and mask wearing to rein in the pandemic.

She 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".

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 taking the public health and social measures aimed at halting transmission for "the rest of this year at least".