Monday, the World Health Organization's chief scientist, Soumya Swaminathan, advised against people mixing and matching coronavirus vaccines from different manufacturers.

She said it is a "dangerous trend" since there was little data available about the health impact.

"It's a little bit of a dangerous trend here. We are in a data-free, evidence-free zone as far as mix and match," Swaminathan told an online briefing.

"It will be a chaotic situation in countries if citizens start deciding when and who will be taking a second, a third and a fourth dose."

Earlier Monday, the Director general of the WHO, Tedros Adhanom, said that the Delta COVID-19 mutation has been detected in more than 104 countries across the world.

Adhanom added that this variant is expected to be the dominant strain worldwide.

Also Read: Delta COVID-19 strain detected in more than 104 countries: WHO