this is bbc news with the latest headlines for viewers in the uk and around the world. my name is mike embley. the world health organization insists the astrazeneca vaccine is still a vital tool in the global fight against coronavirus, after concerns in south africa about its efficacy. on the eve of his second impeachment trial, lawyers for donald trump ask the us senate to dismiss the charges against him as unconstitutional. myanmar�*s military flexes its muscles — water cannons are used on those protesting last week's coup, but the unrest does prompt promises of a fresh election. a change in policy on yemen the us calls for an end to the war. we get rare access to see

the damage inflicted in the six years of conflict. offered money not to move — china seeks to curb lunar new year travel to keep virus cases under control. hello. the world health organization says it's too early to write off the astrazeneca vaccine, and that it still has an important role to play in the fight to control the coronavirus. that's after a disappointing day when a study in south africa found that the vaccine was not proving to be as effective as researchers had hoped against a new variant sweeping the country. astrazeneca hopes it will have an adapted vaccine ready by the autumn. the next phase of the pandemic could become a game of catch up between the variants and the vaccines. our science editor david shukman has more. around the world, there is now a race between the virus and the vaccines, between the threat of new variants and efforts to stay ahead of them, and the outcome

matters to us all. while a first wave of countries, including the uk, should see the majority of their populations vaccinated this year, others won't reach that stage till next year, and many will have to wait for the year after, or even longer. this is a global virus, it's a global pandemic. until we are all protected, then it could be that a variant in another country mutates, so that the current vaccines are no longer effective, and that will come back, so even those people who are vaccinated, they are still going to be at risk with these future variants. the virus is changing all the time, and when it infects human cells, it takes over and gets them to make millions of copies, but they will not all be the same. each batch may have some random genetic mistakes, mutations that are usually unimportant, but a few might prove dangerous.

so the first task is to track these changes, and that is done by studying the genetic code of the virus. since december 2019, when it was first confirmed in wuhan, scientists have monitored what effectively is a family tree, with hundreds of different branches. each of these lines represents one of many different variants that has emerged over the course of the past year. it is only by doing this genetic research that we can spot the variants that are worrying, in the uk, brazil and south africa. half a million british coronavirus samples have gone through genetic screening so far. these machines are among those that have done most of the analysis. but few countries can work on this almost industrial scale, so there is a lot we don't know about how the virus is changing worldwide. there are thousands, millions of cases globally. there are undoubtedly other variants of covid that are spreading quickly that we are just blind to, and any one of those additional

strains around the world could confer an advantage for the virus, allow it to re—infect people, even though they have been vaccinated, and that is what we want to protect against. one answer is to have a global screening operation. in west africa five years ago, mobile labs studied the ebola virus. something far larger is needed now, and alongside that, the faster the vaccines can be rolled out and adapted, as new variants emerge, the safer we will all be. david shukman, bbc news. lawyers for donald trump filed a more detailed brief on the eve on the former president's impeachment trial. they called the case against him an act of "political theatre" by democrats. mr trump is accused by democrats, and a handful of republicans, of inciting the attack on the capitol on january 6. senate majority leader chuck schumer announced that he had agreed

a structure for the process with the republicans and hoped it would lead to truth and accountability. following the despicable attack onjanuary 6, there must, there must be truth and accountability if we are going to move forward, heal and bring our country together once again. sweeping something as momentous as this under the rug brings no healing whatsoever. let's be clear about that. chuck schumer there. let's speak to our north america correspondent david willis. david, mrtrump david, mr trump has had some trouble getting and holding a defence lawyer. to this thing in more detail? —— what are they saying? in more detail? -- what are they saying?— in more detail? -- what are they saying? in more detail? -- what are the sa inc? ., , , ., they saying? donald trump is to refer to these _ they saying? donald trump is to refer to these proceedings - they saying? donald trump is to refer to these proceedings as i they saying? donald trump is to refer to these proceedings as a l refer to these proceedings as a witch hunts, hoaxes, and that is the tone struck by his lawyers in this deposition they filed today for some they've basically called the democrats action in active political theatre, they are making the

point that is all part of a continuing political vendetta, if you like, against donald trump, and they're particular on procedural matters here rather than specifically the merits of the case against donald trump. challenging the constitutionality of bringing impeachment proceedings against somebody who is no longer in office. they make the point that donald trump is now a private citizen, although there is nothing in the constitution that says that somebody who has left office cannot be tried in this way. now, democrats have said that the evidence against donald trump is overwhelming. they filed a brief of their own last week, 80 pages in total, but donald trump himself has refused to agree to turn up and give evidence on his own behalf. that means that this trial could last a lot less, could be a lot shorter than the previous impeachment trial of

mr trumpjust over a year previous impeachment trial of mr trump just over a year ago, which lasted three weeks, of course. . , course. david, what is the likely timetable? - course. david, what is the likely timetable? much i course. david, what is the likely timetable? much of| course. david, what is the - likely timetable? much of that, i suppose, depends on whether they're going to be witnesses or not. it they're going to be witnesses or not. ., , , . they're going to be witnesses ornot. .,, , . or not. it does very much so, make, or not. it does very much so, make. and — or not. it does very much so, make. and it _ or not. it does very much so, make, and it all— or not. it does very much so, make, and it all gets - or not. it does very much so, make, and it all gets under. or not. it does very much so, i make, and it all gets under way around lunchtime tomorrow, that is tuesday, we are going to have four hours of debate over the constitutionality of these proceedings, followed by a vote, and if the majority votes in favour of continuing the proceedings, then there will be 16 hours allocated in total to each side to present their case over the course of two days. both prosecution and defence, if you like. and then you mentioned witnesses. that will require a vote, if either sites decide they want to introduce witnesses, and then there will be summary arguments, and we could have some sort of verdict in this case as long as, as

early as next week. it would require two thirds of the senate to actually impeach donald trump, to find him guilty of inciting insurrection. that would require 17 republicans to cross the aisle, something which i have to say seems highly unlikely, given the current political circumstances. david, we will be _ political circumstances. david, we will be back _ political circumstances. david, we will be back to _ political circumstances. david, we will be back to it. - political circumstances. david, we will be back to it. thank i we will be back to it. thank you very much for that. the price of bitcoin has increased by more than 10% after the electric car manufacturer, tesla, said it had invested $1.5 billion in the digital currency last month. on that announcement, bitcoinjumped to a record $47,000. the value has doubled since the beginning of the year. this time last year, the value of bitcoin was around $7,600. the value of other cryptocurrencies such as ethereum and xrp has also increased. glen goodman is a bitcoin expert and author of the crypto trader. hejoins me now.

thank you very interesting up for us here in london. what do you make of this? what has tesla done exactly and why? what elon musk has done is really a publicity exercise more than anything else. 1.5 alien dollars might sound like alien dollars might sound like a lot of money, but to distil than 10% of tesla's overall cash reserves, so it is significant and if the price of bit —— macron were twofold or medically compelled be a problem for tesla because they have to declare a loss if the price falls. but, and this is the bad bit about the accounting, if the price rises, they cannot declare a profit on they cannot declare a profit on the price, they have to sell the price, they have to sell the bitcoin to get that profit, but at less than 10% of their overall cash reserves, it is not the end of the world. as i

say, is a pr exercise partly but also showing that he has confidence in the future of bitcoin and reptile currency in general. d0 bitcoin and reptile currency in ueneral. ,, ~ , general. do you think it is some kind _ general. do you think it is some kind of _ general. do you think it is some kind of game i general. do you think it is i some kind of game changer for some kind of game changerfor crypto currencies in general? i crypto currencies in general? i do, actually, and i don't usually say things like that. i'm usually pooh—poohing things, but i do think in this case it will be a game changer, because in the long—term, with such an enormous company setting this president, that they are to put their cash reserves in a relatively unproven commodity like factor one, as opposed to things like gold which are more traditional, having done that, it would then encourage lots of other big companies who have been digging about it but were a little bit scared and now they will be thinking, if elon can do it, nobody�*s going to blame us if we do same thing —— unproven commodity like bitcoin. ., ~

bitcoin. elon musk has been in trouble for. — bitcoin. elon musk has been in trouble for, is _ bitcoin. elon musk has been in trouble for, is he _ bitcoin. elon musk has been in trouble for, is he doing - bitcoin. elon musk has been in trouble for, is he doing the i trouble for, is he doing the same thing again?- same thing again? yes, i reckon- _ same thing again? yes, i reckon- l— same thing again? yes, i reckon. i do _ same thing again? yes, i reckon. i do not - same thing again? yes, i reckon. i do not want i same thing again? yes, i reckon. i do not want to l same thing again? yes, i- reckon. i do not want to label him because i do not know for sure... �* , ., him because i do not know for sure... 2 ., �* sure... let's not. butl suspect— sure... let's not. butl suspect that _ sure... let's not. butl suspect that is - sure... let's not. but i suspect that is what i sure... let's not. but i| suspect that is what he sure... let's not. but i i suspect that is what he is doing, yes. suspect that is what he is doing. vee— suspect that is what he is doing, yes. suspect that is what he is doina, es. ., ., , ., doing, yes. he has got a bit of a habit of— doing, yes. he has got a bit of a habit of picking _ doing, yes. he has got a bit of a habit of picking up _ doing, yes. he has got a bit of a habit of picking up crypto i a habit of picking up crypto currencies such as doge coin, invented for a joke, a meme, but it is also an actual crypto currency, and now the price is going through the roof because elon musk keeps tweeting about it over and over again. he has also put #bitcoin on his twitter profile. i do not know how much, if any, he personally owns, but certainly must have known that if the company invested in bitcoin and then announced it, it was bound to do good things for the price. thank you.

presidentjoe biden has called for an end to the war in yemen, which has killed around 100,000 people according to one un estimate. it's been six years since a saudi—led coalition intervened in the country's civil war, to restore an internationally recognised government to power. but houthi rebels, backed by iran, are fighting to regain control. the bbc�*s international correspondent orla guerin has had rare access to yemen. a warning, you may find some parts of her report distressing. aden, a city cradled by mountains in a country overshadowed by war. it's the seat of power of yemen's internationally recognised government, which is propped up by saudi support. but when ministers flew in from exile in riyadh, this was the welcome. the first of three missiles slamming in. screaming

the woman screaming in fear is a localjournalist, alia fouad. i saw fire. and i saw so many people running on the ground, kids, women injured, killed. for a moment, ithought about my family. yemen's foreign minister, ahmed bin mubarak, saw the full horror from the plane, along with the rest of the newly—formed unity government. i was very optimistic. i hoped to return to the country, start, you know, the process.

as the foreign minister, it was top of my agenda to start preparing for the peace process and, you know, dealing with all of these other challenges. we never thought that we're going to have such an attack. but in just 60 seconds, 21 people were killed, including aid workers and airport officials. the government blames iranian—backed houthi rebels who control most of yemen. they deny it. the news was broken on this tv channel by their reporter at the scene.

adeeb al—janani was killed on the spot, on one more dark day for yemen, leaving behind five young children. "he died, died, died," says his mother, who had begged him not to go. she was having so many plans... and in another home in aden, another room full of absence. she used to have one lovely smile. yasmine was one of the 18 people killed at the airport. she was yemen's deputy minister for public works. do you have any thoughts, any words, for the people who would carry out an action like this? yeah, i have...

it's not only our family that lost a really beloved person. it's around... i don't know, each and every house definitely have someone they lost. i'm sure whoeverjust did this thing, i am sure also that he has lost someone in his family. so i'm just saying, let's talk. can the conflict be stopped? it's deeply embedded here and it's playing out against a backdrop of regional rivalries. the new us president, joe biden, is pushing for peace. he may need to be ready for the long haul. orla guerin, bbc news, aden. do stay with us on bbc news. there is much more to come, including this. curbing celebrations to keep out coronavirus — china offers to pay citizens not to travel for lunar new year, usually the biggest mass migration on the planet.

there's mr mandela, mr nelson mandela, a free man taking his first steps into a new south africa. iran's spiritual leader, ayatollah khomeini, has said he's passed a death sentence on salman rushdie, the british author of a book which many muslims say is blasphemous. the people of haiti have flocked to church to give thanks for the ousting of their former president, ba by doc duvalier. because of his considerable value as a stallion, - shergar was kept in a specialj secure box in the stud farm's central block. shergar was driven away. in a horse box the thieves had brought with them. there stepped down from the plane a figure in mourning — elizabeth ii, queen of this realm and of all her other realms and territories, head of the commonwealth, defender of the faith.

welcome back. very glad to have you with us on bbc news. the latest headlines for you... the world health organization insists the astrazeneca vaccine is still a vital tool in the global fight against coronavirus, despite concerns in south africa about its efficacy. on the eve of his second impeachment trial, lawyers for donald trump have asked the us senate to dismiss the charges against him as unconstitutional. protests against the military coup in myanmar have spread across the country for a third day. there have been some clashes between the security forces and demonstrators. the commander—in—chief of the military has spoken out for the first time on television —

justifying his actions. the bbc�*s nyein chan aye reports from yangon. chanting sending a message to the generals. for a third day, anger has brought tens of thousands of people out onto the streets. worried about the future of the country, the people here say that their freedom has once again been taken away. this generation did not think they would have to do the same resistance against the military rule. young people hoped they would grow up in a very different myanmar, open to the world and its possibilities. but now they find themselves battling to restore democracy and end military rule, just like the generation before them. but that fight won't be easy. their leader, aung san suu kyi, is still under house arrest. and today, the general who put her there spoke for the first time since taking power.

ong sans justifying the coup, he said civilian leaders had failed to hold a proper election last november. across the city, red shirts hang outside homes in support of the protest movement. inside one apartment, this family say they have been protesting against military rule for three generations. for them, history has a way of repeating itself. 44—year—old thet thet aung spent four years in prison for protesting. translation: i feel really bitter about this coup. i "so it happens again," i said in my heart. i can't sleep thinking that our new generation will suffer this again. some here arejoining protests for the first time. this student, who can't show his face for safety reasons,

spent most of his adult life in this young democracy. so the thing i don't like about the military takeover is everything. i feel like we have no freedom. i feel like we have lost our freedom at home. as the protests build, the military is already starting to tighten the grip on the country. despite mass demonstrations in many cities for days, there is still no sign that the military will back down. nyein chan aye, bbc news, yangon. let's quickly round up some more of the main news. israel's prime minister has pleaded not guilty to charges of bribery, fraud and breach of trust. benjamin netanyahu was making his second appearance in court since his trial began in may last year. he was charged over

allegations that he accepted improper gifts and sought to trade favours with media moguls in exchange for positive coverage. mr netanyahu has called the charges "fabricated and ludicrous". in a tit—for—tat move, germany, poland and sweden have expelled russian diplomats in response to russia's removal of their respective representatives over the weekend. all three countries, and the eu, deny claims that they participated in demonstrations supporting russia's jailed opposition leader, alexei navalny. hong kong is expected to decide shortly whether to grant bail to the media tycoonjimmy lai. he has been accused with colluding with forces under the new security law. he is the highest profile figure arrested since the law came into force lastjune. a popular, previously uncensored social media app called clubhouse appears to have been censored in china. users of the american audio—only app have been experiencing disruptions, with some speculating that it has been put under the same restrictions imposed by chinese authorities on other

social media sites. the lunar new year begins at the end of this week, as families across asia celebrate the arrival of the year of the ox. in china, that usually means millions of people making their way home to celebrate with theirfamilies. it's the world's biggest mass migration. but this year, after a year of tight controls to keep covid infection down, many are having to stay at home. shanghai's railway station is usually frantic at this time of year, but not this time. robin brant reports. china is the land of big numbers, and it's this time of year in particular when you get the biggest numbers, chinese new year spring festival — chunjie, as it's known in chinese. this is the biggest mass migration of humans on the planet and they move over a month—long period, mainly from china's cities out into the rural areas. right, let's look at those numbers. on average, you tend to get about a50 million people moving in that month—long period. this year, though, the government estimates it's going to be different. they see a drop in passenger numbers of 20% compared to last

year, a drop of 60% compared to the previous year. this is all about trying to prevent another national outbreak of covid across this country. there is intense pressure from the government, and it's doing it by carrot and stick. let's look at the carrot first. in some cities, you get 1,000 rmb — that's about $160 — if you decide to stick around over the next few weeks. but if you're determined to go and see your family and you leave shanghai, well, this is what you face, multiple tests — a covid test before you leave, monitoring where you are in your destination, a covid test before you come back and monitoring when you get back.

now, this isn't scientific, but based on what we're seeing here this morning, people are staying away. this is much more quiet than what i would usually see at train stations at this time of year. it's going to have a big impact, particularly on tens of millions of migrant workers, people in the construction industry, for whom this is the only time they get to go home and see their partners and they get to see their children. those people are going to have to wait another year before they can do that again. robin brant for us there. spare a thought for people in northwest canada. a pullerfor texas brought in record breaking temptress to manitoba, saskatchewan and alberta. temperatures as low as minus 40.9 celsius. cold enough? instantly freezes water. extreme weather warning seven issued for much of this week.

there is more for you on the bbc website. and on the twitter feed. thank you for watching. hello. very cold out there at the moment, with ice around and of course further snow flurries, particularly in eastern areas. the heaviest of those snow flurries as we go through tuesday, covered by a met office amber weather warning across parts of central scotland. travel, power, communication disruption possible, as those snow levels start to mount up. but it's notjust that, it's the extent of the chill this morning. may be as low as around —14, —15 through some parts of central scotland. all starting the day sub—zero. you can see where those snow showers line up through central areas of scotland. there will be others around northern and eastern parts of scotland, and we'll see little snow corridors again across parts of england and wales, just focusing some of those snow showers to give a further covering in some places. either side of it, we will see

just that light flurry most of you saw through tuesday, but a better chance of some sunshine in between. you saw the winds, another windy day across the board. in the thermometers, temperatures barely above freezing — it's going to feel much, much colder than that. and with some of the strongest of the winds to be found down toward south—west england and the channel islands, it's here where the coldest wind chill values will be found, as cold as —10 through —8 through the afternoon. also the chance of some sleet and snow very close to cornwall and the channel islands to end the day. that will gradually pull away as we go through the night and into wednesday. a subtle shift in wind direction means snow showers pushing through southern scotland into northern england in particular, and a few lines further south. another icy night, temperatures could get even colder, —15, —16. now, the big picture to start wednesday has low pressure out in the atlantic trying to get towards us, but high pressure is holding on. and with the isobars opening out a little bit, the good news is it's not going to be quite as windy on wednesday. those winds more north—easterly, so it will be parts of south—east scotland, north—east england, the focus of showers. a few down east anglia, the south—east too, but more

of you dry on wednesday, more of you see the sunshine. it's not going to do much to the temperatures, still struggling to get above freezing in some spots. another widespread, harsh frost, then, to take us into thursday. plenty of sunshine around for many, but increasing cloud into the west. signs of weather fronts trying to push in as the breeze picks up. signs of something milder trying to edge in as well, but do not underestimate the power of cold air across europe. it could hold off that charge of milder air from the west and could stay cold for many of us right the way through into next week. bye for now.

the latest headlines from bbc news... the world health organization �*s warning against jumping to conclusions about the efficacy of coronavirus vaccines. this is despite a south african study that suggests the astrazeneca jab mac is less effective against the virus. organisations say it is an important tool. former president donald trump's lawyers have asked to dismiss charges brought against him, claiming they are unconstitutional. he's charged with inciting insurrection when he urged his supporters to march on the capital building. five people died in the violence that followed. myanmar�*s military will address the nation for the first time since the army sees power last week. the general says subject vow civilian leaders failed to bold a proper election.