UK takes new measures to slow Omicron coronavirus variant

Britain's Prime Minister Boris Johnson speaks as he holds a press conference on the new Omicron coronavirus variant, in London, Britain November 27, 2021. Jeff Gilbert/Pool via REUTERS

LONDON (Reuters) -Britain announced new measures on Saturday to try to slow the spread of the newly identified Omicron coronavirus variant and a top health official said there was a "reasonable chance" that vaccines could be less effective against it.

Prime Minister Boris Johnson said arrivals from all countries would have to self-isolate until receiving a negative result from a PCR test, that face masks must be worn in retail settings and it was time to step up booster jabs.