>> announcer: this is "nbc nightly news" with lester holt good evening, everyone the wait for a covid vaccine for the youngest americans may soon be over moderna today says it's asking the fda to green light its vaccine for children under 6. approval of a two-dose shot would extend covid protection to the last group of currently ineligible americans, the very young. delays in fielding a vaccine for young kids have proven frustrating for many parents, especially as more americans drop their guard against the virus. according to the american academy of pediatrics, covid cases in younger children have increased by 43% over the last two weeks moderna says trials suggest its vaccine is less effective than the adult version but does well preventing severe illness stephanie gosk has more on today's announcement >> reporter: a year and a half after the first covid-19 vaccine for adults was authorized, moderna now says it has a version for children ages 6 months to 5 years old that is safe and provides robust protection >> when we look at effectiveness, we see excellent level of antibody in these children. >> reporter: the vaccine is two shots taken four weeks apart. 25% of the adult dose. the company says it is 51% effective for ages 6 months to 2 years and 37% for ages 2 through 5. those numbers only tell part of the story, according to a doctor who helped conduct the trial. >> there was no severe disease or hospitalizations observed within the trial. but we did see some infections. >> reporter: amber rodriguez enrolled her twin 4-year-olds, in part to protect vulnerable adults in the family >> it was really important for us to get our kids vaccinated as soon as we reasonably could. >> reporter: but a majority of parents of young children appear much more tentative. >> i'm not sure. i might wait for other kids to get it first. >> i think it's not necessary at this moment. >> reporter: only 28% of kids ages 5 to 11 have gotten two doses of the vaccine the fda could authorize moderna's pediatric vaccine as early as june. the cdc says 75% of children 17 and younger have contracted covid medical experts recommending even children who were infected with omicron should be vaccinated. >> number one, we don't know how long infection-induced immunity lasts number two, vaccines don't just protect against the variant that they had. they can protect against future variants. >> reporter: now after a long wait, the youngest among us ma soon get that protection. >> stephanie, what about pfizer will they be looking for a similar emergency use authorization for their pediatric vaccine? >> reporter: yeah, lester they will. they're expected to ask for that eua in the spring their dosage is less than moderna but the course is three shots instead of two lester >> stephanie gosk with that news tonight, thank you. this evening in ukraine, the capital kyiv coming under renewed attack just as the u.n. secretary-general was visiting the city, while in eastern ukraine, russia is stepping up its assault. kelly cobiella is there with late details. >> reporter: late tonight, two explosions and the desperate scramble to find survivors under the rubble after new strikes in kyiv. ukrainian officials saying two buildings were hit a stunning bombardment on the city soon after the united nations secretary-general met with ukraine's president and toured kyiv's devastated suburbs, seeing the toll russian forces left behind before they retreated weeks ago. >> there is no way a war can be acceptable in the 21st century. look at that >> reporter: and tonight there are new signs russia's assault is gaining momentum in the east, including this strike in donetsk and another in zaporizhzhia in kherson, now under russian occupation, a television tower struck though it's unclear who's responsible for that attack then there's besieged mariupol the u.n. secretary-general said president putin told him this week he agreed in principle to a rescue plan. but today inside the steel plant where ukrainian soldiers and civilians are still holed up, ukraine's national guard putting out this video it says of people desperately digging wounded soldiers from the rubble after a makeshift hospital was hit with a concrete-busting bomb. in the ruins of the city, 100,000 people tonight the mayor told me russian soldiers won't let them leave "all the people who escape, they use only one word to describe it, hell there's no water, no electricity, nothing locals are forced to clear bodies from the streets in exchange for food and water," he said. in russian he said, "the decisions are made by one man, he decides who lives and who dies." >> kelly joins us again from dnipro. kelly, we're getting late word about russian military movements near mariupol what can you tell us >> reporter: that's right, lester. a senior u.s. defense official says tonight there are signs that some russian forces are moving away from mariupol, toward the northwest. and all indications tonight are that they still don't have total control of the city. lester >> kelly cobiella, thank you. let's get now to that new aid package for ukraine worth $33 billion that the president is asking congress to approve. kristen welker is at the white house. kristen, the president clearly wanting to send a message to russia in all this >> reporter: that's absolutely right, lester president biden announced that sweeping, new ukraine aid package with a warning to russia, aggression will not win, threats will not win. the price tag is a massive $33 billion. more than double the entire aid that congress approved last month and includes ammunition, armored vehicles, and humanitarian aid in a sign the administration is bracing for a prolonged conflict, the package is aimed at lasting five months the challenge now, how quickly can they get this through congress, with ukraine urgently pleading for more help as russia intensifies its assault. congressional democrats say they want to link ukraine assistance to funding to fight covid, but republicans say that's a no-go. the president announced new sanctions against russian billionaires today and a plan that would make it easier to seize the assets of oligarchs. lester >> kristen welker, thanks questions this evening about that dramatic prisoner exchange between the u.s. and russia. a marine veteran held for almost three years is home, but another american is asking why he was left behind andrea mitchell now with the latest. >> reporter: tonight, marine veteran trevor reed home in texas for the first time in nearly three years after being freed from a russian jail president biden agreed to a prisoner swap for a convicted russian drug smuggler serving 20 years in the u.s. >> we believe that he probably saved our son's life. >> reporter: the two prisoners trading places between american and russian planes on a tarmac in turkey overnight reed was serving a nine-year sentence for allegedly assaulting two police officers in moscow held in what the family describes as squalid conditions, they say causing urgent health issues. >> he looks terrible to us. as a parent, we know he does not look well. he's very thin. >> he was walking strange, looked like they had to help him get up into the airplane. >> reporter: their son receiving medical care at a military hospital other americans jailed in russia are still waiting. basketball superstar brittney griner, arrested on drug charges in february. businessman paul whelan, another former marine, has served more than three years of a 16-year sentence. he spoke to his family last night from prison >> one of the first things he said was, why was i left behind? there's not a good answer for that. >> what hope do you have of getting him back >> my dad's 85 my mom's 83. as each day ticks by, there may be fewer opportunities for them to actually see paul ever again. >> reporter: the u.s. says whelan is being held on false accusations of spying. >> espionage charge is clearly designed to extract some benefit from the united states, no question about it. >> reporter: u.s. officials say russia arrests americans on trumped-up charges just to have hostages to trade when they want to get a russian back lester >> okay, andrea. thank you. a rally on wall street the dow, s&p, and nasdaq all up. it comes on the heels of some surprising economic news. new data showing the u.s. economy shrank in the first quarter after strong growth at the end of 2021. it's the weakest performance since the start of the pandemic. tom costello on what's behind it. >> reporter: tonight, further evidence of the economic paradox americans are living with every day strong consumer demand is sending prices skyrocketing for everything from groceries to gas to cars to travel and unemployment is at 50-year lows with plenty of jobs available. still, the economy actually shrank 1.4% in the first three months of the year the president insists the january omicron surge played a big role. >> what you're seeing is enormous growth in the country that was affected by everything from covid and the covid blockages that we incurred along the way. >> reporter: analysts say the economy unexpectedly contracted because the government cut back on pandemic-related spending and the u.s. imported more goods than it exported america buying more than it sells overseas meanwhile, the war in ukraine and china's new covid lockdowns are worsening the global supply chain crisis in south carolina, nephron pharmaceuticals is now building its own production plants since it can't get enough supplies from overseas it also has hundreds of job openings but must offer high wages and very flexible hours to attract workers. >> come whenever you want, stay as long as you can or as short as you can, and we try to pay at the end of the shift. >> reporter: the fear tonight, with higher prices, higher housing costs, the higher wages, the fed poised to raise rates again, the country could be pushed into a recession. >> you've got workers that finally got out of the cold and into the warmth of rising wages, and now they're getting burned by inflation. having to take on an extra job to make ends meet >> tom, given today's economic news, does that change expectations that the fed will raise interest rates next week >> reporter: analysts generally still believe the fed will raise rates by half a point next week and continue raising rates this year because it needs to get inflation under control. but higher rates mean new loans, mortgages, rents, and credit cards will get more expensive as well, lester. >> meanwhile, tom, apple and amazon both reported earnings after the bell today what do those reports tell us about where the economy is >> reporter: apple had good numbers out but said that supply chain issues from china may persist through the year amazon reported slowing sales as americans start to get back to their pre-pandemic shopping habits >> a lot to cover tonight on the economy. tom, thank you. in 60 seconds, gun deaths at an all-time high in this country and the ban on menthol cigarettes in the works. how it could save hundreds of thousands of lives a disturbing new report tonight on gun violence analyzing cdc data, a study by johns hopkins university found overall gun-related deaths increased by 15% in 2020 to more than 45,000. that's the highest number ever recorded by the cdc firearm homicides soared by 35%. 2020 also saw a record number of gun sales. tonight, a major move to ban the sale of menthol cigarettes. the plan by the fda is aimed at saving hundreds of thousands of lives and would have a big impact on black smokers who use them most heavily. we get more from rehema ellis. >> reporter: the fda has talked about the dangers of menthol cigarettes for years today the agency is proposing to ban them. >> the proposed product standards would, among other things, improve the health and reduce the mortality risk of current smokers of menthol cigarettes or flavored cigars. >> reporter: menthol makes up one-third of all cigarettes sold in the united states, and a ban would overwhelmingly impact black and young people >> i was planning on quitting anyway. >> reporter: research shows 85% of black smokers use menthol cigarettes, compared with 29% of white smokers. the cdc says smoking is the leading cause of lung cancer, and black men have the highest rates of that disease. if this ban goes through, how significant would it be in terms of affecting the health of all americans >> this is a landmark regulation that fda is proposing. our projections are that 1.33 million smokers would quit among whom 381,000 would be african american smokers. >> reporter: tonight altria group, the parent company of some leading tobacco manufacturers, saying in part, taking these products out of the legal marketplace will push them into unregulated criminal markets that don't follow any regulations and ignore minimum age laws the fda proposal could go into effect in a year, but it's expected the tobacco industry will fight it, which could lead to a long court battle rehema ellis, nbc news. up next, our series "climate challenge. inside california's drought emergency. the difficult choices farmers face and how they impact the u.s. food supply. back now in our los angeles studio with our series "climate challenge." the drought emergency here in the west lake mead, the country's largest manmade reservoir, is only about one-third full, a historic low it's so bad in colorado that the agriculture department declared the whole state a primary natural disaster area, unlocking aid for farmers and ranchers one of the problems, not enough snow. that's also a huge issue here in california where the ripple effect is severe >> reporter: in california's san joaquin valley, these are days of hard choices for farmers. >> we had to cut out actually a couple of crops, and we've had to cut back on our melon program. >> reporter: joe delbosce has operated his farm since 1985. >> this i think is the worst year we've ever had. >> reporter: he's right. water officials believe the past three years could end up as the driest in california's history >> i look over here and i see a beautiful day by the lake. what do you see when you look at this >> i see a dangerously low reservoir. we are at ground zero for the california drought. >> reporter: the state's reservoirs are alarmingly low this is lake castaic north of los angeles sitting at 53% capacity to give you perspective, in good times the water should be nearly to the top of that dam. california's natural resources secretary, wade crowfoot, says the snowpack in northern california's sierra nevada mountains says it all. what do the last measurements tell you? >> the last measurements are pretty grim. we have a lot less snowpack than we've had in the past due to hotter winter temperatures then due to hotter spring and summer temperatures, more of that snow is either absorbing into very dry soils or evaporating into warm air. >> reporter: just this week, a water supplier to 6 million southern californians declared an emergency, severely limiting nonessential water use. the drought impacting parched farmlands and american dinner tables. >> the tomatoes, the sweet corn, melons, things that we would normally have at the stores aren't going to be grown in the quantity this year than we're used to >> reporter: california provides two-thirds of the u.s. supply of fruits and nuts >> we're blessed with this mediterranean-type climate here in california that nobody else has and we can grow crops here that can't grow anywhere else. >> reporter: farmer bill dietrich grows tomatoes but not now. >> no tomatoes this year because this water has got to be put to use on other crops that, for us, is less risky. >> reporter: many farms partly rely on groundwater, but if it's not stored in the good years, it can leave fields like this high and dry in the bad years. now state officials are under pressure to do something we've heard from farmers who complain that there's not enough being done to capture the water that falls during the good years. >> well, they have a good point we have to do more to ensure that when we do receive these large winter storms that we're capturing water. not only in our surface reservoirs but pumping that water back underground so, for example, we are investing billions of dollars in recharging groundwater basins those are infrastructure projects >> reporter: time may have run out. >> we're not looking down the road five years or ten or 20 years. and what we're seeing is a diminished capacity to feed our own people and that's the tragedy here we don't have the water to grow the food that we could be growing here that makes it to the store that we all shop at. >> reporter: hard times, hard choices. but for joe delbosce, an unshaken belief in this land. >> i never fail to just love what i see when we're planting. see some plants there in this great soil, these soils and this area produces some of the best melons in the country. and i'm very proud to be a part of that. >> water a major challenge here in the west. up next, we'll introduce you to a hero dance instructor who is now leading daring rescue missions in ukraine test. finally, he went from teaching kids dance to making trip after trip to rescue children from a war zone matt bradley now with one of ukraine's heroes >> reporter: not all heroes wear capes. some wear dancing shoes. we met nazar shashkov who ran a ballroom dancing school in mariupol it wasn't so long ago you were using this to bring kids to dance competitions >> yes, it was my big dream for a long time. >> reporter: but russia's invasion changed his tune for weeks he used this same van on daring drives into the besieged city to get his students and their families out. >> it was fragment of shell that had ricocheted from floor and get here. >> shrapnel? >> shrapnel, yes and this - >> this was broken. >> reporter: facing russian checkpoints, land mines, artillery shells you could have driven yourself out of there, never gone back. >> yes, yes. >> why didn't you do that >> because of the kids. >> reporter: nazar said he couldn't sleep, thinking about his kids trapped in mariupol collecting rainwater to drink, cooking over open fires he made multiple trips rescuing nearly 100 students and their families, like maxim and his mother if it weren't for nazar, do you think your life might have been in danger >> yes, of course, because two days after we left mariupol, our house was burned >> this is the first of my students and they grew up with me and all our school grew up. we made it together. >> reporter: nazar's old school now destroyed. but with his students safe, he's determined to keep dancing. matt bradley, nbc news, zaporizhzhia, ukraine. >> remarkable. that's "nightly news" for this thursday. thanks for watching. i'm lester holt. please take care of yourself and each other. good night right now on nbc bay area news tonight, it's not over. we have new details about that bizarre kidnapping in san jose. this story changing by the hour. what our sources and court documents are revealing about how this plot unfolded. plus -- the boy's mother speaking at the courthouse today in san jose. what she is feeling now that her son is back and the two people suspected of the kidnapping are in jail. and here we go again. prepare to mask up. bart's new rules, and what happens if you break the rules. and some people vowing to leave twitter. is it you? if elon musk's takeover is actually happening. we're looking into the politics of the potential twitter exodus.