cnn's athena jones is in new york city. tell us more about this new vaccine requirement. >> reporter: well, this is a big step that city officials hope will make a big difference. we've heard the mayor stressing this over and over again. that he wants to focus on vaccines. on getting more people vaccinated. just yesterday he stopped short of bringing back reinstituting an indoor mask mandate. he has said in the last few days he wants to focus on the thing that will make a difference, vaccinations. that is why they're taking this big step, going further than any city. this will have a slow rollout. it will be enforced september 13th. it requires proof of vaccination to go into restaurants inside, for fitness centers, jips and indoor entertainment venn view. -- venue. people only have to prove one shot. the proof can be a vaccine card. it can be nyc safe app, and new york state already has an app