London: UK Prime Minister Boris Johnson on Sunday warned of a looming “tidal wave” of Omicron, and brought forward a target to give over-18s a booster jab by one month to the end of December.

Britain began easing Covid-19 restrictions in June and the alert level was at stage three, which means the epidemic is in general circulation.

Level four means “transmission is high and pressure on healthcare services is widespread and substantial or rising”. The four chief medical officers for England, Wales, Scotland and Northern Ireland said the move was prompted by advice from the UK Health Security Agency, a public health body.

Omicron is spreading much faster than Delta and that vaccine protection against symptomatic disease from Omicron is reduced. Data on severity will become clearer over the coming weeks but hospitalizations. Infection rates remain stubbornly high at about 50,000 positive tests per day. In London, Omicron accounts for about a third of all Covid-19 cases from Omicron are already occurring and these are likely to increase rapidly.