this is bbc news. i'm james reynolds with the latest headlines for viewers in the uk and around the world. 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 prompts promises of a fresh election. a change in policy on yemen the us calls for an end to the war there. we get rare access to see the damage inflicted

in the six years of conflict. can the spacecraft reach the planet mars? it reaches its riskiest point in the rendezvous. hello and welcome. 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 have filed their 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. speaking on the senate floor ahead of the trial, the majority leader chuck schumer — who's from the democrats — 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. our washington correspondent lebo diseko explains how this will play out. we have had from donald trump's lawyers a welcome of that bipartisan agreement, even if they did use echoes of their client's language there, saying that this is still an unconstitutional impeachment trial. in terms of the rules that they have set out, they'll start out with a debate and then a vote tomorrow on that issue of constitutionality. i guess the question is over whether or not you can impeach somebody who is no longer in office. it's kind of an echo of the same vote that we saw when the senators were sworn in not long ago.

and you'll remember five republicans voted with the democrats to allow that, so we are likely to see this go ahead as planned. then, the two sides will have 16 hours each to present their case. they can have up to eight hours over two days. they are going to break on thejewish sabbath because one of donald trump's team is an observantjew, and then there is a provision for the democrats, if they want to, to have a vote on witnesses. there is a feeling both sides would like to see this wrapped up fairly quickly, within a week or so. if they bring the witnesses, that will bring it to a slightly longer time. we could see it go on for quite a bit longer, actually. and of course the judges, thejurors on this, the senators, are actually witnesses themselves. they are, indeed, you might

say, victims in this case. does the defendant himself have to show up? well, he's said that he will not. we don't know whether there will be a move to subpoena him. that is something that the senate can vote to do. whether or not donald trump would abide by that, we don't know. i think it's unlikely we're going to see them go down that road, but the house impeachment managers who are acting as the prosecution said that donald trump's refusal to turn up is something that will be borne in mind. that is something that will reflect bad on him, they say. for the first time in a presidential impeachment process, a sitting president is not taking part. what does the biden administration think of what is going on in the senate? i thinkjoe biden would rather we be focusing on something else. i have been watching the twitter feed all day, both him and the white house tweeting about the economic rescue plan he has for coronavirus. that's what he would like us to be focusing on, and instead we're talking

about his predecessor. he has said that he is going to leave it to the senate to decide what to do. he is focusing on running the country. but it's not an ideal situation for him at all. lebo diseko reporting. 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 but, so far, protests have been largely peaceful. the coup leader, 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. 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. - 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 his 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. stay with us on bbc news. still to come: curbing celebrations to keep out coronavirus — china offers to pay citizens not to travel for the lunar new year, usually the biggest mass migration on 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 fate. this is bbc news. the latest headlines: 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. 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 local journalist, 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. let's get some of the day's other news now. israel's prime minister, benjamin netanyahu, has pleaded not guilty to charges of bribery, fraud and breach of trust. he was making his second appearance in court since his trial began in may last year. mr netanyahu 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. 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. storm darcy has brought severe weather conditions to much of the uk, with heavy snow and ice across eastern regions of england and parts of scotland. it's the coldest snap since the so—called beast from the east struck in 2018. schools and vaccination centres have been forced to close

in some areas, with police warning people not to travel, as helena wilkinson reports. a bus driver struggled to keep control. such were the challenging conditions on the road. in norfolk, some abandoned their cars as snow drifts stopped them from getting through. emergency vehicles were also affected. kent has had some of the heaviest snowfall, up to 16 centimetres in some areas. this scene has been repeated across much of eastern england. due to storm darcy, we had some strong winds, which has caused a lot of drifting in some areas, and that's caused a lot of problems on the roads. the aa says numerous

accidents have been caused. in chartham in canterbury, local workers helped to keep village life ticking along. we don't want anyone snowed in, so why not help at the community? the weather forced some vaccination centres to close, including several in suffolk and essex, as well as surrey and norfolk. coastal towns like southend—on—sea in essex were amongst those to experience the full force of the adverse weather. as well as heavy snowfall, it has been bitterly cold, temperatures are expected to drop to —10 overnight in some parts of england, and the next few nights are set to be the coldest of the winter so far. helena wilkinson, bbc news, southend—on—sea. the united arab emirates' historic first mission to mars will soon be arriving at the red planet. the hope probe launched from japan lastjuly and will study the planet's weather and climate but one of the most dangerous parts of its journey has to take place successfully first. our global science correspondent rebecca morelle has more. a first for

the united arab emirates. this was the moment last summer when it sent its spacecraft to mars. now it's almost reached its destination, but the probe, called hope, has a critical manoeuvre ahead — getting into orbit. it needs to approach mars at just the right speed and angle. if anything goes wrong, the entire mission will be lost. we don't really want to hit the planet, nor do we want to pass by the planet. we need to be very precise with how the operation happens. the hope mission will see more of mars than we've ever seen before. its spacecraft has an elliptical orbit, swinging in closer and then much further away. at its closest, its flight matches the rotation of mars, so it hovers over some key features like olympus mons, the biggest volcano in the solar system. at its furthest point, the planet spins beneath it,

giving it a much wider view. this means it will see almost all of the planet from both close up and from far away. the spacecraft will study the atmosphere to solve a big mystery of how mars transformed from a planet with water, like earth, to the dry, dusty world it is today. until now, the uae has only sent satellites into earth orbit. arriving at the red planet will be a huge leap. to know that there is a spacecraft that has gone from this region further than any man—made object has ever gone, that is hurtling towards a small pink dot that you also see in the sky, i can't describe the feeling or the thought process, but i never thought that this was possible. the spacecraft has one shot to get into orbit. if it succeeds, history will be made, firmly establishing the united arab emirates as a new space power. rebecca morelle, bbc news.

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. our china correspondent 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 in shanghai. a reminder of our top story. the world health organization has warned against jumping to conclusions.

warned againstjumping to conclusions. the s or zeneca vaccine... you can reach me on twitter. do stay with us. 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.

this is bbc news. the headlines... the world health organization has warned against jumping to conclusions about the efficacy of coronavirus vaccines. if after a south african study suggested that the astrazeneca jab is left effective against local variants —— less effective. expert said the vaccine is still an important tool. donald trump's lawyers have asked to dismiss charges against his —— and his impeachment trial. he's been charged for inciting insurrection. myanmar�*s military ruler has addressed the nation for the first time since the army sees power last week. the general said civilian leaders failed to hold a proper election and promised fresh polls later on this year.

now on bbc news, it's time for a