The World Health Organization expects to have more information on the transmissibility of the new omicron variant of the coronavirus within days, its technical lead on COVID-19, Maria van Kerkhove, said in a briefing on Wednesday.

That was faster than the "weeks" the WHO had predicted last week that it would take to assess the data available on the variant after designating it a "variant of concern," its highest rating.

Whether the variant is more transmissible or evades vaccines are some of the major questions that still need answering.

Vaccine developers have said it will take about two weeks to assess whether their shots are effective against it.

Van Kerkhove said one possible scenario was that the new variant, which was first reported in southern Africa, may be more transmissible than the dominant delta variant. She said it was not yet known if omicron makes people more ill.

WHO chief scientist Soumya Swaminathan said the agency believes the existing COVID-19 vaccines will work against the variant.

Mike Ryan, WHO's emergency director, reiterated the agency's opposition to the blanket bans on flights to and from southern Africa that have been imposed by Britain and other countries, saying it would not prevent the variant's spread:

"The idea you can just put a hermetic seal on some countries is not possible. I can't see the logic from an epidemiological or public health perspective."