we do begin this hour with encouraging news for the country worst hit by the coronavirus, but also a crucial, crucial warning. the u.s. is powering through vaccinations. cdc data shows that 1 in 5 americans have now received at least one dose, and more than 1 in 10 are now fully vaccinated. but spring break is here, and many states are easing back on restrictions. travel is picking up to the level it was a year ago. and people are letting their guard down. perhaps adding to an overall sense of relief, americans are starting to receive those $1,400 stimulus checks as well from the biden administration. so it may feel like the u.s. is emerging out of a dark winter into a hopeful spring. but experts still pleading with the public to stay vigilant. here s paul vercammen with that, paul? reporter: coronavirus restrictions are loosening up from coast to coast, but one of the nation s top health experts is warning governors, if there was ever a time to put on a mask, this is it.