Scientists believe they may have found the "trigger" behind the extremely rare blood clot complications stemming from the Oxford/AstraZeneca vaccine.

       The team - in Cardiff and the US - have shown in exquisite detail how a protein in the blood is attracted to a key component of the vaccine.

       They think this kicks off a chain reaction, involving the immune system, that can culminate in dangerous clots.

       Professor Alan Parker, from Cardiff University's School of Medicine, said: "[This] only happens in extremely rare cases because a chain of complex events needs to take place to trigger this ultra-rare side effect."

       "We hope our findings can be used to better understand the rare side effects of these new vaccines - and potentially to design new and improved vaccines to turn the tide on this global pandemic," he added.

       A spokeswoman for AstraZenaca told the BBC: "Although the research is not definitive, it offers interesting insights and AstraZeneca is exploring ways to leverage these findings as part of our efforts to remove this extremely rare side effect."

       Follow the latest updates below.

       A drug treatment which, the makers say, works against the new Omicron variant of Covid-19, has been approved by UK regulators, reports our Breaking News Editor Gareth Davies.

       Xevudy (sotrovimab), made by pharmaceutical giant GlaxoSmithKline (GSK), has been found to cut hospital admission and death by 79% in those at risk.

       The monoclonal antibody has been authorised by the Medicines and Healthcare products Regulatory Agency for people with mild to moderate Covid-19 who are at high risk of developing severe disease.

       It comes as GSK and Vir Biotechnology said preclinical data shows the drug "retains activity against key mutations of the new Omicron Sars-CoV-2 variant".

       The UK Government has ordered around 100,000 doses of the drug.

       You can read Gareth's report in full here.

       Japan has reversed a ban on new inbound flight reservations, revealing confusion between government agencies and the public over Prime Minister Fumio Kishida's strategy to keep out the omicron variant.

       On Monday, Japan's aviation bureau told airlines not to accept new reservations for December over omicron, two cases of which have been found so far, but the abrupt move provoked worries among those aiming to return for year-end holidays.

       Mr Kishida said the move caused confusion, and Chief Cabinet Secretary Hirokazu Matsuno added that the prime minister had asked the transport ministry, which oversees the airline industry, to keep in mind the needs of returning Japanese.

       Airlines may now take new reservations as long as arrivals stay within a daily limit of 3,500, down from last month's figure of 5,000, a transport ministry official said.

       On Monday, Mr Kishida banned new foreign entrants to Japan, unwinding border opening measures that started last month. Later, the ban widened to foreign residents of Japan arriving from 10 African nations, where omicron was first identified.

       On Thursday, transport minister Tetsuo Saito told reporters the aviation bureau had "responded speedily from the standpoint of emergency and prevention", although without reporting to him.

       He added, "I told the aviation bureau to respond carefully to the matter that greatly affects people's livelihood."

       The United States has announced its first confirmed case of the Covid-19 omicron variant had been detected in California, in a fully vaccinated traveler who had recently returned from South Africa and was recovering from mild symptoms.

       Top health official Anthony Fauci said authorities "knew it was just a matter of time" before the strain was found in the country, reminding Americans that vaccination, boosters and masking in indoor public settings remained the best way to stay protected.

       According to a statement by the Centers for Disease Control and Prevention (CDC), the person returned from South Africa on November 22, and their close contacts have all tested negative.

       Speaking to reporters, Dr Fauci added that the patient tested positive on November 29, and that they had not received a booster, to the best of his knowledge.

       "We feel good that this patient not only had mild symptoms, but actually the symptoms appear to be improving," he said.

       While the person involved was fully vaccinated, Dr Fauci stressed a Covid booster remained a good idea because it raises the number of overall antibodies in a person's immune system, some of which will remain effective at stopping new variants.

       "Our experience with variants such as the Delta variant, is that even though the vaccine isn't specifically targeted to the Delta variant, when you get a high enough level of an immune response, you get spillover protection," he said.

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