GENEVA, Nov 25 (AFP) - COVID-19 vaccines reduce transmission of the dominant Delta variant by about 40 per cent, the WHO said on Wednesday (Nov 24), warning that people were falling into a false sense of security concerning jabs.

The World Health Organization's director-general Tedros Adhanom Ghebreyesus said many vaccinated people were wrongly thinking the jab meant they no longer needed to take any other precautions.

Fully-immunised people must stick with measures to avoid catching the virus and passing it on, Tedros insisted, spelling out how the more contagious Delta meant the vaccines were not as effective against transmission.

"We're concerned about the false sense of security that vaccines have ended the pandemic and people who are vaccinated do not need to take any other precautions," Tedros told reporters.

"Vaccines save lives but they do not fully prevent transmission.

"Data suggests that before the arrival of the Delta variant, vaccines reduced transmission by about 60 per cent. With Delta, that has dropped to about 40 per cent."

The more transmissible Delta variant is now overwhelmingly dominant around the world, having all but out-competed other strains.

"If you are vaccinated, you have a much lower risk of severe disease and death but you are still at risk of being infected and infecting others," said Tedros.

"We cannot say this clearly enough: even if you are vaccinated, continue to take precautions to prevent becoming infected yourself, and infecting someone else who could die."

That meant wearing a facemask, maintaining distance, avoiding crowds and meeting others outside or only in a well-ventilated indoor space, he said.