Dr. B, a website launched by a team of experts that includes ZocDoc CEO Cyrus Massoumi, connects eligible adults with leftover COVID-19 vaccines at risk of expiring. This can happen if a person misses their vaccination appointment or extra doses come in a vial, for example.
"Ultimately, patients need this vaccine, and there's providers who need help getting it to the people of priority," Massoumi told the New York Times. "That's my motivation."
More than 1 million people signed up for the service as of Wednesday morning. It's free to use, and any American over the age of 18 can sign up.
After completing a profile on hidrb.com, people on the list may receive a text message from Mr. B when local verified providers let the service know about leftover doses.
Recipients must respond to the text message within 15 minutes and be able to arrive at the vaccination site at a set time.
Nearly one in 10 Americans -- more than 32 million people -- are now fully vaccinated against COVID-19, according to data from the Centers for Disease Control and Prevention. States are working to ramp up their vaccination efforts, hoping to get more shots into more arms faster.
CNN Wire contributed to this report.