<b>Live updates: follow the latest news on </b><a href="https://www.thenationalnews.com/coronavirus/2021/11/29/omicron-live-updates-covid-variant-vaccine-test-cases-travel/"><b>Covid-19 variant Omicron</b></a> Millions of Britons have been bit by more uncertainty since the <a href="https://www.thenationalnews.com/coronavirus/2021/12/12/omicron-spreads-faster-and-weakens-vaccine-immunity-says-who/" target="_blank">Omicron Covid-19 variant</a> was discovered in the UK and many fear another lockdown is on the horizon. Could Prime Minister Boris Johnson impose drastic measures again, despite warnings from businesses that they risk going under? Mr Johnson and <a href="https://www.thenationalnews.com/tags/sajid-javid/" target="_blank">Health Secretary Sajid Javid </a>have both refused to rule out a nationwide shutdown as the country battles a new wave of Omicron. In an address to the nation on Sunday, Mr Johnson declared an “Omicron emergency” and brought the booster vaccine target forward by a month to offer every adult in England a shot before the new year. He stressed that a third dose of a coronavirus vaccine is necessary to protect against Omicron, as a wave of the variant hitting an unvaccinated population risks “a level of hospitalisation that could overwhelm our NHS and lead sadly to very many deaths.” He suggested that booster shots were the UK’s only line of defence against Omicron and that if the accelerated campaign does not prove effective more restrictions could be necessary. Mr Johnson urged everyone to step forward for a third dose, arguing it was vital to “protect our NHS, our freedoms and our way of life.” Ministers are said to be drawing up a “Plan C” for a further tightening of social restrictions if the Omicron outbreak severely worsens over the Christmas and New Year period. A fourth national lockdown could be on the cards for millions of people in England. The devolved administrations in Scotland, Wales and Northern Ireland make their own rules. While a nationwide shutdown is considered the most extreme measure, and the most damaging for the economy, the prime minister may be pressured into imposing one if the NHS looks like it will buckle under the strain of an Omicron wave. Prof Neil Ferguson of Imperial College London, whose modelling was instrumental in the government’s decision to impose the first lockdown, said ministers may have no choice but to lock down again. However, he said the government's work-from-home advice, which came into effect on Monday, would slow the spread of the variant to allow the country to buy more time to vaccinate the population. “There is a rationale, just epidemiologically, to try to slow this down, to buy us more time principally to get boosters into people’s arms, because we do think people who are boosted will have the best level of protection possible, but also to buy us more time to really better characterise the threat,” he said. Last week <a href="https://www.thenationalnews.com/world/uk-news/2021/12/11/uk-at-risk-of-75000-omicron-deaths-unless-tougher-restrictions-imposed/" target="_blank">a group of scientists advising the government said the wave of Omicron gripping the UK could lead to 75,000 more deaths in England</a> unless tougher restrictions are brought in. Experts from the London School of Hygiene and Tropical Medicine, part of the University of London, used experimental data to look at how Omicron may be transmitted over the next few weeks. The team, whose members sit on the UK’s Scientific Advisory Group for Emergencies, said their research indicates that “Omicron has the potential to cause substantial surges in cases, hospital admissions and deaths in populations with high levels of immunity, including England.” Last week Mr Johnson announced England would be moving to Plan B, which includes mandatory face masks for most indoor public settings, a work-from-home order and vaccine passports for nightclubs and mass events. On Tuesday, he is set to face a possible rebellion from MPs in his own party when the package of measures goes before the House of Commons for a vote. Asked about opposition to the plan within the Conservative party, Mr Javid refuted the idea that vaccines give people a false sense of security because they can still contract Covid and pass it on after being jabbed. He said anyone who is not vaccinated will have to show a negative Covid-19 test result to gain entry to clubs, which would further reduce the chances of Omicron spreading. “For any high-risk event if someone has taken a lateral flow test and it’s negative that means that individual is less likely to be infectious than otherwise,” he told BBC Radio 4's<i> Today </i>programme. On Sunday, the chief medical officers for England, Scotland, Wales and Northern Ireland raised the UK’s Covid Alert to level four, the second highest level. Raising the bar means the epidemic is “in general circulation, transmission is high and direct Covid-19 pressure on healthcare services is widespread and substantial or rising”, according to government guidance. The decision was taken following advice from the UK Health Security Agency (UKHSA) and recent data which showed Omicron cases are doubling every two to three days. On Sunday a total of 3,137 Omicron infections were declared in the UK — a 65 per cent increase from Saturday's total of 1,898. Dr Susan Hopkins, the chief medical adviser for the UKHSA, said more restrictions may be needed to dampen the spread of the variant, which was first discovered in the UK last month. She said ministers will have to make a “very difficult” decision on whether to impose more curbs on top of the Plan B measures announced last week. “I think that the restrictions that the government announced are sensible,” she told the BBC. “I think that we may need to go beyond them. But we'll need to watch carefully what happens with hospitalisations.” The last time Britons lived under Level 4 was in February when the mixing of households, hugging and sports were banned. Schools were also shut, along with hairdressers, non-essential retail outlets, cinemas and theme parks. The government had issued a “Stay At Home” order which meant people were allowed to venture out only for essential work, to buy necessities, obtain health care or exercise.